The mechanism of Hide My Folders resembles a screen: files and folders stay intact in their places on the hard drive, but they are not visible from the OS, as Hide My Folders provides a kind of “cloak” to them.
So, there is no way of losing access to the hidden folders/files. All you have to do is to boot under another OS to see the files. If you have disabled Hide My Folders driver in Safe Mode (in Options), it will be enough to boot in Safe Mode to see the files you hid.
Besides, if Hide My Folders is deleted or uninstalled, all the files/folders will become visible.
In case your Windows system crashes, you will find all the hidden files visible when you reinstall the OS on the target PC.
Note: Since Hide My Folders is a “cloak” which hides the files/folders only in the OS it was installed under, the files will become visible if you move the hard drive with the hidden files to another PC.