Help! vista reset everything and lost alot!

Hi!
So just a few days ago, my computer was just fine, I had my my music playing on my iTunes, I had access to my word documents, and had everything going well. However, just a few days ago, there was a blackout while my computer was still on. And, some time soon, I decide to turn my computer back on again. But then when I logged in, it said "Preparing your desktop," and I knew something went really wrong.

Then, my desktop appeared, my usual pure-black background and some icons for some applications. However, icon sizes were changed and many were missing. So then I decided to listen to some music. But when I clicked on iTunes, it asked me to install it. So this proved that something went REALLY WRONG. I went to my documents, and sadly, all my precious documents were GONE. All photos, EVERYTHING. It was as if my Documents, Music, Pictures folders were somehow reset. However, my files in Admin. were still fine, untouched. I went to DOWNLOADS in my Admin. folder and everything was still there.

To check if my hard drive deleted alot of stuff, I went to my Computer, and i checked the amount of space left in each HDD and everything seemed close to what I remember when I last checked.

Everything works out fine, but then my computer is now twice as slow and I need to reinstall everything, despite the fact taht they were still intact. Seems like all my programs has been hit with the "RESET" button.

Im not asking much, but I wish that I could get my Documents back.
Is there anyway?

Thanks for reading and please give me some directions of what I could do to get my stuff back.
Thanks!

CPU: AMD Athlon X2 4600 2.4GHz
MB: ASUS M2N68-AM
RAM: OCZ Reaper 4GB DDR2
HDD: 80GB, 500GB
OS: Windows Vista Ultimate