[willichadv]

I booted my computer up today, and saw my background wasn't available anymore. Then I see the message, "Warning! Spyware detected on your computer! Install an antivirus or spyware remover to clean your computer". It says that Win32/Adware.Virtumonde and Win32/PrivacyRemover.M64 are on computer.

[Elvandil]

The warning is from spyware, too. They want to sell you something.

You need to run your anti-virus and anti-malware scanners. Be sure to use more than one for malware. If you need help, you need to go to the Malware forum, read the sticky, and post a log.

By "background", do you mean your wallpaper?

Free anti-malware scanners:

A-Squared
Spybot S&D
RunScanner
Ad-Aware 2007
SuperAntiSpyware
Spyware Eliminator
Emco Malware Destroyer
Spyware Doctor
Arovax Anti-spyware
Trend-Micro Rootkit Buster
F-Secure Blacklight
Bootzilla (Bootable antimalware CD with many other tools.)

List of freeware security software