Jamesfranklin, the above tips will be useful going forward to the future, but here is what you can do now:
1) Get an anti-virus program, install it and let it run. Here is a link for AVG Anti-virus Free Edition: WWW Link
2) Since your computer is already infected, the anti-virus program might not be able to fix it. If that is the case, go to WWW Link
and run the Trend Micro Housecall, an on line scanner. Post the results and we might be able to help you.