Bad virus on computer. Can't use system restore. Trying to format.?

-no idea how i got this virus. I haven't downloaded anything and wasn't on any sites. Then all of a sudden it came up with "avast is infected " then what i'm guessing is a fake "shield pro" thing came up and started scanning my computer, and the desktop went blue. system restore is blocked and just wont open and so is anything else i try from windows. I have a format floppy disk but i disconnected that drive ages ago. I'm trying to just install XP again to see if it overwrights it but it's just asking which partition i want to use, then when i select it it's saying there's already a system on there. Can someone give me a solution? I don't mind if i lose everything there's nothing i wanna keep anyway. I'm just worried it's got my bank passwords or any online account passwords.In the installation screen where you choose the hard disk, there should be a little eraser icon on the bottom of the window that says format, click it and everything will be erased, then just install windows anew.
If you really want a 100% clean system you should reformat it. Otherwise, try AVG 2011 or other anti-virus software but it may or not give you a 100% clean system
A clean installation consists of removing all data from your hard disk by reformatting your hard disk and reinstalling the operating system and programs to an empty (clean) hard disk.



To boot from your CD/DVD, the BIOS settings on your computer must be configured to do this. On start up keep tapping either F1, F2, F10,(Be Aware that some manufacturers use F10 for system recovery!) Esc, or Del, to enter the BIOS set-up. Look for "Drive configuration", "Boot order" or similar and make the CD/DVD drive the first boot device and the hard drive second. Save settings and exit.



Insert the CD/DVD into your CD/DVD drive, and then restart your computer.

When you see the "Press any key to boot from CD" message, press a key to start the computer from the CD/DVD.



Follow the instructions on the screen to select and format (NTFS) a partition where you want to install Windows.



Follow the instructions on the screen to complete the Windows Setup.



Get some Anti-Virus protection and update Windows!



漏 arou42
If you can still use the internet then try this on-line scanner which is free, or it seems the free trial is free :

http://www.eset.com/us/online-scanner.

Or on start up continually click F8 on to get into "safe mode with networking" and download Malawrebytes free version:

http://www.malwarebytes.org/products/mal鈥?/a>

Then update it if necessary and run a scan. If you can`t download it on your desktop then download it on another machine, put it on a usb stick and then plug the stick into your desktop and run it that way.

One of those options should work. Reinstall is the last option I would think.

Hope that helps you, Bob.
Avast is worse than useless. If you can, download Microsoft's free AV. See link.