If I'm not mistaken, I believe that Avast Free will still support XP with SP3 installed.
I could be wrong though.
EDIT: Yep, Avast has a free XP support version here:
You might not get the achievements but Steam can be run in "offline" mode.
I think if you just fire up Steam and not have the system plugged into the internet, it will prompt you with some warning that it can't communicate with the online server, and would you like to start Steam in offline...
That is very odd! I just looked and this PC and it seems to have a ton of work available. That could be due to me having 2 days worth loaded up on these systems. I'll check the other systems shortly to see if any of them are having issues on downloading work.
Check with some thrift stores, flea markets, garage sales, etc... A lot of times you can pick up an ole system from 8 to 10 years ago that will still be running Windows 98 to XP.
Plus, they are kind of fun to mess around with. :p