I need to know which is lighter on this system:

Pentium 233Mhz MMX

128MB PC-66Mhz

40GB HDD

DVD/CD-RW (pulled from another machine)

These are the two anti-virus I am looking at:

Avast!

or

AVGFree

I need to know which has the litest memory footprint and which requires less CPU Cycles to do active-protection

I need these to be in free mode though.