I have a virus on my pc, Iwant to erase everything and start from scratch, however i dont want to be unistalling the OS and reinstalling it cause it takes to long, is there a way I can erase everything but still keep my OS on my pc?

I can not get ride of rootkit pop up ,I know it is sort of virus or spyware
but According to Norton ,and Microsoft I have to scan , It will not let my Norton to scan, also tried some of those Malware or Registry cleaning programs either they do not work or they are not effective ,any IDEA ??please help
my operating system in Windows VISTA

What causes for having a registry problem? is it a virus? and How this registry cleaner fix my registry? any advice what registry cleaner is good…

My friends computer has become infected with spyware or a virus. He is running Windows XP on a Compaq. Theres a little dialog box popping up constantly that says theres a virus on the computer. When you click on the box it redirects you to a spyware remover page. Obviously its an attempt to sell this product. How can I remove this and stop all these pop ups? I was thinking about manually cleaning the registry. How would I go about that? And what about those programs in the Add/Remove programs in control panel that just wont go away? I need to get this junk off his computer. What do I do? Without spending money that is.

I have been having sever data corruption issues with the game World of warcraft. i have run every diagnostic software known to me including checkdisk (windows xp sp3) Microsoft’s memory diagnostic tool and seagates hard drive diagnostic tool both windows and bootable CD versions and every diagnostic comes back squeaky Clean and ive even swapped my ram entirely. I have done a full system restore on my computer and i still cant get a stable install which leads me to believe i have a hard drive issue yet it passes every test. so basically my question is as stated above, is it possible for a hard drive to be going bad yet not fail diagnostics. If so is there any way to verify or at least gather further evidence that its the hard drive before i spend money on a new hard drive. (note it appears as if only world of warcraft is currently effected, i suspect its highly complicated file system is more likely to be damaged by a failing hard drive)
i have installed all patches and all blizz will tell me is its a hard drive issue or a ram issue. and it cant be a virus as i JUST reformatted my hard drive. i have also updated every driver in my system. and while its not a data coruption issue limewire shuts down when i attempt to preview a file