My computer corrupts every software downloaded on shut down?

[exeter]

I've always used THE latest of
AVG,Malwarebytes,SuperAntiSpyware and they're still installed
2 months ago, i bought a laptop and i had no problem using it and have since been working with it. Few days ago, i noticed that: For any software i download to my system, on shut down...it can no longer be useful. What do i mean?
If i download google talk or any other software for instance, i can use them with ease for at least that browsing session or as long as the laptop remains open and running but the moment i shut down or restart, i would have to re-download every one of these softwares otherwise, they become useless.
For the record, I've used window xp and other versions for years without issues but i just bought a new laptop that runs on vista if that helps.
I need the best help i can get. PLEASE THE BEST HELP I CAN GET PLEASE

[Pocpoc]

Did you installed any program like Deep Freeze for example ? ( It's instantly protects and preserves baseline computer configurations , i mean no matter what changes a user makes to a computer, a restart will eradicate all changes and reset the computer to its original state ).
Have you tried a System Restore, to restore it back in the days everything was good ?
Also try do a scan with Spybot Search and Destroy is free.
One more thing you could do is to repair windows with the install cd, maybe it will work.

[vexx]

Have you tried running the SFC (System File Checker) utility in Vista?

[Simsin]

I had this problem too once. I haven't tried what you guys are saying here, i just reinstalled windows