There are a couple of free Anti-Virus programs that are reputable, the one that comes to mind being AVG. However, it seems that a lot of software that was once free/open-source is moving toward the "software as a service" model where you pay a subscription and have to download every new version, rather than for a boxed copy that just updates its definitions.
Others may have their opinions, but the built-in Windows firewall is probably sufficient, especially if your ISP provides a firewall at your Cable/DSL/Whatever modem/router. Don't know if ZoneAlarm still has a free version or not.
OpenOffice is also an excellent alternative to MS Office, if you don't have or want to fork down the cash for a copy.
The bloatware that comes with many new computers can be rather headache-inducing. That's why I stay away from large companies like Dell, who are the worst. When I get a new computer, I make sure that I have an actual install disc for the operating system of choice, and start fresh. The "recovery" discs are coaster ware.
You can usually buy things like office on Ebay still in the shrink wrap. They may be the previous version but MS has add on to get you going. I am running XP pro with Office 2000 and the add on to handle the docx files. I think the Office was $10. You can usually find the OS install disks for that kind of money too. It will work as long as you have the matching COA sticker with the secret number.