Hopedot VOS won't suit most people, but there are some that could find it useful. It would take extended testing [& monitoring], likely over a number of days to tell how well it does when it comes to app & driver compatibility, as well as how much of a trace it leaves behind from running different software inside of it. Installing VOS creates a virtual hard drive -- most of the app's files go there, on that virtual drive, & once you register the software that info's apparently stored there as well -- IOW you might want to set up however many VOS disks as you'll want or need today. Each time you run setup it can create a new virtual disk with it's own set of passwords -- when you run setup it creates a desktop shortcut, & clicking that runs the virtual disk you last installed. You can run each virtual disk separately [individually] using the launcher included with the virtual disk.
WHen you start or launch Hopedot VOS it installs a couple of 32 bit drivers which are responsible for mounting the virtual drive holding most all of the app's files. It won't work in 64 bit Windows unless you launch it from a 32 bit VM [Virtual Machine], & it doesn't remove those drivers once you close it -- they & their related registry entries get left behind. Hopedot VOS is not a full OS, but relies on the copy of Windows that's running when you launch it. Because this is the Secure version of Hopedot VOS you have to go through a import/export procedure to get any files in or out. What it might be good for is as a possibly easier alternative to using something like Truecrypt virtual drives to store a VM or a nested OS [e.g. Windows] install.
If/when you read about nested Truecrypt OS installs the main idea is that if someone finds the outer layer(s) they'll hopefully overlook the innermost OS & have no idea or proof that it exists -- Hopedot VOS [like Truecrypt] will install to a USB device that can be hidden or destroyed, & without it there's no proof it exists [microSD cards are fairly easy to hide or get rid of]. I don't see that much of a reason to install Hopedot VOS to a USB device otherwise, since to run it you have to find a PC/laptop with 32 bit Windows [most likely XP] that is configured to let you use USB and install drivers -- enough restrictions to IMO seriously limit portable use.
I monitored today's GOTD install/setup in my XPMode VM... 3 sets of passwords need to be created/recorded, one for the app & virtual drive, one for the VOS account, & one for "Data Security Management" -- the 1st password is the one used when starting or launching. Running Setup adds a folder to Username\ AppData\ Roaming or Username\ Application Data, a Hopedot folder to Windows, & the 2 drivers to Windows\ System32\ Drivers -- those drivers are responsible for the relatively few entries added to the registry. Everything else went onto the USB stick I used for the virtual drive -- there's a small launcher app, & a SUHopedotVOS folder that holds the virtual disk drive along with 4 other files [including the 2 drivers]. Uninstalling Hopedot VOS Security removes the drivers, though some registry entries are left over, & it also deleted the virtual disk I'd set up. The the total of 6 files can be moved or copied for backup, but the virtual disk itself won't compress with 7-zip -- the .7z file is actually a bit larger than the virtual disk you started with.
FWIW, for portability & privacy there are no truly ideal setups... A good portable app won't write anything to the host's hard drive(s), but Windows will record the fact you ran it, & many public or school or company PCs won't let you use USB in the 1st place [Cameyo modified apps stored on-line *may* work when USB doesn't, *IF* you can download, access, & run them]. A WinPE or LiveXP disc/USB device can work off a ram drive created when you boot using one of them, & that ram drive will go away when you shut the OS down, but you won't always be able or allowed to re-boot if/when it's not your PC/laptop. You can put a complete OS [e.g. Windows] in a VM along with whatever apps, but you need the VM Host software installed & running in whatever OS to use it. There is an unofficial launcher to make VirtualBox portable -- scripts add the needed drivers to Windows, then remove them when VBox is closed -- & I've used it running WinPE or LiveXP as well as regular Windows, but again you have to be able to use USB or a CD, & either re-boot into WinPE etc. or be able to install drivers, which will leave traces.