Oh dear sounds bad! Of course you can get rid of the virus with some help. First - how do you know you have a virus? Has your antivirus software told you? If so I assume it is having trouble fixing it. Let me know what antivirus you have and what name does the virus have. Virus's don't usually cause systems to shut down or change the display. This is typical behaviour for a trojan. If so then someone could be controlling your PC remotely. Whether it is a virus or a trojan I'd recommend going to
http://www.moosoft.com/thecleaner
and download their tool called the cleaner. It is free for use for 30 days. It should detect and fix just about every virus/trojan known. If that all works then you should use XPs go back feature to recover any system changes the virus has caused. If as is possible you've actually got a trojan on your system then please understand that any data you have is now compromised - passwords, bank/credit card details etc. Hopefully not the latter but certainly your internet passwords. Change them. Also there is every chance that whoever has compromised your computer has put some nasty stuff on it. This could be any sort of illegal content. This is what people do so that their nasty stuff isn't on their systems so finding them/prosecuting them is next to impossible. Another favourite trick is to use a hijacked system to launch attacks on other systems (called denial of service attacks) or to operate as a relay to send out spam. Hopefully you have a simple virus but you really must check and clean it off because you are almost certainly infecting others. Hope this helps. Let me know how you get on.