Protect your computer, PLEASE!

First, windows users, get the latest
Windows Updates

Also, you may want Windows XP SP2. For Windows XP users, follow this link:
Windows XP SP2 and click Download SP2 from Microsoft Update

Another major thing, you may want Microsoft Office updates, especially if you are going to use Outlook. Follow this link:
officeupdate.microsoft.com

This is good for protecting against spyware:
Windows Anti-Spyware Here

And for free virus protection, follow the download directions here:
AVG Anti-virus. There is a free version to install here.

And for free spyware blocker, beyond Windows Defender, (a good idea) follow the download directions here: (English link)
SpyBot