First, try to update it to v1.52, then do the online updates and run the immunization tool.
Then, in go to the Mode Menu and switch from Default Mode to Advanced Mode. Once there you will have access to several advanced tools, including one that controls your system startup items (color coded for easy use- green for okay items, yellow for okay but unnecessary items, and red for items that should be immediately disabled). There is also a tool for IE BHOs (browser helper objects)- a lot of malware takes advantage of the BHO system to perpetuate itself). Next is a System Internals tool that checks for bad registry entries.
There are also other freeware programs such as HijackThis (a registry editor that focuses on internet-related entries), and SmitFraudfix.exe (a handy tool that should be run from Safe Mode).
On top of all that, you also need to make sure you have a good, up to date antivirus program. I always recommend McAfee, but others here also have their favorites and will be glad to let you know what they are.
That's a basic beginning, but it's ONLY the beginning of the process. A more advanced virus-slaying technique post is HERE:
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=242x18605Please note that the very first thing you need to do is BACK UP YOUR IMPORTANT FILES TO AN EXTERNAL MEDIUM. This usually means either burn a series of cds or copy everything to a second hard drive. Do this first, and then do this often.
Have fun!