Great advice above, and here is more to think about
:
1-any time Windows does an update, its possible for some of the tweaks to get reset back to the wrong way(something to keep in mind for the future).
2-"all of a sudden" implies that something has changed. This could be any number of things such as: a Windows update, any new piece of software or plugin, a virus/trojan/malware(if the computer is connected to the internet),
3-Trashing prefs is often the first thing to try for any "odd" behavior(the computer, not you
). Pro-tools-pc.com offers a very handy utility called Trasher(for Windows users) and its absolutely worth a donation.
4-re the comment about drive failure, you should ALWAYS assume all your drives are ready to fail(because they often ARE). With that in mind, you should be backing everything up on a regular basis. I keep a pair of big(4-6TB) USB drives that do nothing but backups. 1 drive is for drive images and the other drive has copies of every session(plus a partition where I store every installer I download). Even this is NOT a bulletproof backup. To be truly bulletproof, things would be backed up to 1 or 2 more drives, and those drives would be stored in another building
Back to the point about drive imaging, if you save images of your C: drive when things are running great, you can easily restore when bad things happen(the BEST way to recover from a failed drive or a virus attack is to format the drive and load your drive image, which takes all of an hour or two, vs spending 2 days re-installing the OS and every other piece of software you own)