I have a hdd from someone i know and it has vista on it,. i think its really effected bad. its slow, any kind of program i try to open like, my computer or control panel anything like that wont open at all. windows explorer keeps crashing and the cpu is always running at 100%. is there any type of software that can remove viruses before boot up.
Partitioning the drive won't do anything. And formatting the drive should be a last resort.
If it's a slave drive then wiping it clean really isn't a big deal...which is why I asked if it was the primary drive or not. Formatting would be the fastest, most simple and most reliable if it were indeed a slave drive and didn't have an OS on it. And the reason I said to do a partition too is because its always good practice to remap the drive before a format. The fact that he is having issues opening critical system utilities and folders would also lead to believe there might be an issue with the file system and a partition would definitely take care of that.
If you can't get the software that is mentioned in the guide, to install and run in safe mode with networking, then use the AVG rescue disc that is linked in there. It will boot the computer off the disc, and scan the hard drive. You won't need to put your hard drive in danger of also being infected.