I cannot stress this enough!  Make sure you always have the latest windows critical system patches which you can get from Windows Update  and PLEASE get yourself some anti-virus software the free ones are ok but not updated as quick as some of the full paid for versions, believe you me it's worth way more than they charge for these products. I recommend Norton Anti-Virus 2005 and if you don't have a router and you just have your computer hooked direct to a modem, make sure you have a firewall turned on! This is no joke there has been a really nasty virus released the last couple of days and we have been going crazy at work with many systems down at our customer’s stores due to all the reasons above not being addressed. One step further would also be to get some anti-spyware protection as well to block all the junk you get on your computer from many websites out there. Microsoft has a descent one in beta right now which you can read about here so please don't delay any further and get yourself covered today or it may already be to late!