Shutdown/Restart/Log-off problems, on Windows XP

For some reason sometimes when I either shut down, restart or log off my computer, it doesn't even get to the "Saving settings..." page and seems to restart, taking me to the disk check that happens when the computer has not been turned off properly. Please tell me why this is and how I can fix it if you know, as it's driving me ****ing nuts...

You might need to reinstall Windows. =/

Goddamn it... WHY DON'T ANY COMPUTER SHOPS IN THIS GOD FORSAKEN CITY ACTUALLY GIVE YOU THE DISK THEY USED TO INSTALL WINDOWS TO YOU?!

If I do actually manage to get a Windows XP install disk, will reinstalling it effect any files or anything on my system?

Very likely, but since I'm ass-stupid in this subject, don't trust me on that

chances are it'll nuke 'em all, but if you do decide to reinstall i would reccomend that next time you repartition your hd first so that you can stick windows and your programs in one partition while your files stay safely tucked away in another (partition magic is good for this i hear)

and if you do get your hands on an xp install cd and need your current install's key, give me a shoutout

also, here's a little tidbit from annoyances.org on this very issue