Right now we are loading AVG 8.x on machines that are not quite built to run this program (too slow). What is a good free antivirus that would run well on something like 1.0ghz 256mb (or something that is 6 years old)

Avast. Speaking from experience with a 1200 Mhz Duron + 386MB and a PIII @933Mhz + 265MB. Just don't use other background scanning providers than the standard one. Avira is very good but I prefer Avast on older machines.

Redhatcc
Eset Smart Security
it's pretty popular and it's perfect for gamers and low perfomance computers :-)

vaska94, that is not free.

@Redhatcc: avast is your best option.

The following is my opinion, make changes only after determining they are correct for you!

Avast is a good freeware AV and you might get along fine with only the Basic Shield.

If you let Avast, it will install P2P, eMail, Network, and Web protection, if you don't want nothing more than
an AV program don't install them, otherwise you will have 4 or 5 new services and a new process in startup.

If you should need to make any changes to Avast you will first need to disable avast! self-defense module
otherwise you will be pulling your hair out trying to disable anything.

Mike