Your problem is very ABnormal.
Can you save your work?
Make sure that you don't inadvertly do a restore to a previous restore point at each boot!
That would undo any installation you have done, but don't affect saved user files.
Do Start|Run...
Type "msedit"
In the Startup tab, make sure that there is NO restore command active.
Make sure that you ALWAYS properly shut down the computer.
You must NEVER EVER just switch it down. It's a very good way to loose files and to corrupt others.
Next, whenever you install any new hardware and drivers, you ABSOLUTELY need to be logged in as an administrator.
Make sure that the account that you use have the permissions to install new softwares. A visitor account may let you THINK that you installed something, but NEVER allows the installation of ANYTHING!
Don't try to install anything not "portable" to any external disk.
Electro, May 2011