open office is fine for most things and you can find tons of free antivirus software online,even places like aol now have a free antivirus /firewall package .I think its mcafee,
I would get the cheaper versions of office out there,like students version etc.. I wouldn't ever recommend finding a cracked or some pirated version of office with a made up registration number.It can lead to a load of problems with the running of vista,microsoft is master at protecting their software.
open office has been great for me