First, try if you can launch task manager or move process explorer to the PC (rename it to iexplorer.exe). Use this tool to remove security tool : http://www.keep-PC-clean.com/
Also, you can try creating new user on the PC and see if the virus is activated when logging in with that user.
Other option is to try system restore.
A new feature for new Vista to actively prevent and remove spyware is Windows Defender.
Windows defender
Windows defender software
For complete instructions on how to remove windows vista check: www.removevista.com
The reason could possibly be that Windows Vista was an upgrade, and had an upgraded firewall. Windows Vista also had Windows Defender installed by default, however, XP required a download for it. Windows Vista also patched several common exploits in Windows XP which were being used in viruses.
Yes. No operating system is 100% safe from viruses. Vista is one of the safest however. Windows Security Center, Windows Defender, and Windows Firewall, and User Account Control (UAC) are four of the ways in which Vista protects itself from malware.
Windows Defender
Some of the programs that come with Windows Vista Home Premium Service Pack 1 includes Windows Defender, Windows Firewall and Windows Media Center. It also comes with Internet Explorer 7, Windows DVD Maker and Windows Flip 3D.
You can use Windows Defender to disable programs that run at startup, or using System Configuration.
Five policies that are supported by Vista and 7, but not XP are Windows Defender, Windows Security Center, BitLocker Drive Encryption, Parental Controls, and User Account Controls. All versions support Windows Firewall.
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You can not simply downgrade to Windows XP from Windows Vista. If you want to completely remove Windows Vista in favor of XP, you will have to format the hard drive and reinstall the OS from scratch. Windows XP will not install on top of an existing Vista installation.