Video & audio handling in Windows can get very complicated... The Odin Video Converter, while it may indeed work provides a fair example of how an app can negatively impact the media handling ecosystem in the Windows you have installed. To help understand how things got so screwy to begin with, I think it helps to understand the nature of video formats &/or specs -- specs almost always refer to playing audio/video & NOT encoding it, plus they're a bit loose, so anyone & everyone can come up with their own way of doing things & still get a file that [usually] plays when/where it should. Those different methods are pretty often incompatible. That's OK when software keeps its hands to itself, but when it tells Windows how to do something, stuff can easily get broken. What follows is the How as simply as I can put it, but it's still a bit of a slog... Putting the quick summary 1st, at one extreme you have apps like the VLC player or Wonderfox converters that are completely self-contained & either fully portable or very close to it, with Windows not knowing or caring that they're there. These apps can't effect anything else. At the opposite extreme you have apps that are anything but self-contained, that tell Windows to use the media handling code that they provide -- just that part effects Windows & many installed apps, but it gets worse when they use stuff with well-known compatibility problems, & is worse yet when they overwrite what you may already have with older versions, & that's where programs like Odin Video Converter & Super & to a maybe lesser degree Format Factory fit in. Now those apps do work, & many people like them, & it is possible for them to be trouble free, particularly when you don't have/use anything else, particularly when you don't ever use/play incompatible audio/video files. And that's the long & short of it -- if you like an app like one of those 3, aren't really into video, & don't mind tying your hands a bit in the future should things change, you're golden. If you can't answer yes to all 3 criteria, stay far, far away.
TO get more detailed, 1st there are codecs [COmpresser/DECompresser] that get assigned to whatever video file types/formats, some are better than others, & it can be a bit of a chore to set things right again when a lesser codec takes over for a better one you already had installed & working. CodecTweakTool, Win7DSFilterTweaker, InstalledCodec, & sometimes DXMan2 can help. Codecs & other audio/video handling files can be VFW [Video For Windows] or Direct Show, & a single codec may include both. The codec provides the translation into & out of whatever video format, & Windows uses DS [Direct Show] to handle that video, though individual apps may or may not [just like they may use D3D or not]. Codecs & DS files may be used only by the software they belong to, or they can be made available to Windows & every other app installed in Windows -- likewise software may look for & use any codecs &/or DS files that Windows says are available, or it may restrict itself to just the code that came with that app itself. It's not as common, but software can also take a mixed approach, accepting some or all outside codecs &/or DS files, while making some or all of it's own codecs &/or DS files available. It's the shared stuff that can get you in trouble.
When an app uses DS to open a video file, several DS files [filters] are normally involved, with things like a demuxer to split audio & video portions apart, a decoder, possibly filters to change the size &/or translate the colorspace, a video renderer etc... GraphEdit or GraphStudio can show you how your Windows install chains these filters together -- under the File menu there's an option to render or play a video file, & they'll draw the graph with connected blocks for each of the DS filters used. Video software that uses DS does the same thing. But if for example you have 3 demuxers, several decoders etc. all available to Windows, how does it decide which ones to use? When each of those DS filters [files] was installed & made available to Windows, it included 2 things, a list of what it can do [including what media types it can work with], & a relative merit ranking. When software *Builds a Graph* it looks to see what can do the job, then starts with the top ranked DS filter, & if the chain doesn't work it tries another, & another... If/when "Brand X" & "Brand Y' filters are used together, they may not like each other, causing things to break. And if that wasn't enough, say filters a, b, & c are opened to try and fit into one of those slots, but ultimately the d filter was used -- a, b, & c can still be open, ready & waiting to conflict with any of the several other open filters, used or not. That merit ranking then can be pretty important. You can edit the merit using a few apps, including GraphStudio [Graph menu -> Insert Filter] or an app called Filmerit. There's an app called GSpot that may/may not be useful to you as well, showing what filters/files Windows tries to use for audio/video. [You can pick up those free apps mentioned at videohelp.com/tools/ .]
OK, so there's a danger in adding a lot of codecs &/or DS filters to your system, but what else do apps like the Odin Video Converter do that maybe they really shouldn't? Besides installing codecs & DS filters, OVC adds portions of what otherwise would be several complete programs, & outdated versions at that... AND overwriting newer, complete installs. In a word, Bad. It's not unusual for a video app to require other software, & it's not unheard of to include either the required setup files or provide links etc. But adding OVC to your system you 1) add partial versions without the full controls you'd have otherwise, 2) add outdated versions that may have problems with software expecting more current, 3) add partial, older versions of apps with a history of compatibility problems, 4) overwrite/replace the current, full, working installations. Several other apps [e.g. Super] are intrusive but not as bad -- they often take over some stuff, add all or portions of conflict prone apps, but just don't go as far.
When things video break it can be a nightmare to fix, so how do you put things back? Restoring a backup is the only sure fire way. Removing the app gets rid of problem files in the program's folder, but not necessarily anywhere else, & it doesn't restore the files/filters you were using, nor their related registry entries. You can try to find the files causing problems by renaming them *while they're inactive* to make them unusable -- the hard part is locating all the files to begin with. You can also try something like DXMan2, Autoruns, or the 2 utilities already mentioned to disable them. Another potential problem can be your graphics card/chip drivers -- they use universal drivers rather than something matched to your particular card/chip model, so video acceleration/filtering code is included, & that can conflict too... I had a problem a year or so ago that showed up in Windows Media Player with mjpeg files, but I could get the files to play if I turned off hardware video acceleration in Cyberlink PowerDVD. I've had problems in/with wmplayer that went away when I turned off that same accel for DivX in the registry. Neither should have made the slightest difference using a 3rd party mjpeg codec, but they did, & that just shows how delicate or intertwined Windows video ecosystem has become.