If you really want to be sure you won't lose any of your valuable files, get another external disk and copy all the files there. Save it in a separate place, dry and cool, and use it only when you need to update your archives. For maximum security, store it in a separate building. Cloud storages are handy, too, but 300 gigs would be quite expensive and take forever to upload.
Checking what's been saved is quite easy: Right click on a saved folder in your computer, note the amount of files, folders and data. Do the same on the same folder in your external disk. They should match.
A nice tool to make sure everything will be copied from one instance to another is the free
Roadkil's Unstoppable Copier. Unlike Windows, in case of a problem it'll just list a problematic entry and continue from that, allowing you to retry copying the failed files.
After making sure every photo and video is safe on the external disk, I'd do a fresh reinstall, wiping everything away. After the reinstall I'd update everything, remove all temp files and run a defrag. After that I'd do the tweaking. Black Viper knows what he's talking about.
Why do a fresh reinstall?
- You've had three different videocards installed, remains of their drivers may slow your system down if not make it unstable
- Some Windows updates may have been unnecessary/badly coded/replaced with better ones
- Remains of programs you've uninstalled
- Remains of problems you might have had
Yet one hint: I suppose you're running Windows7 which has a good backup tool. You might want to make a couple of backups on your external disk. One from the freshly installed, cleaned but not tweaked, plain vanilla system and another of the setup you feel most satisfied with. The first one will save your time in case your tweaking takes an unwanted course, the second will get you flying in half an hour even after a hard disk failure.
