Ok, if you get a disk with a flashing question mark, then i'm assuming that on the hardware side of things, everything should be ok. What you need to do is to get a known-good Mac OS startup CD and try that. Because you only have 64MB of RAM that limits your choices to 8.6, 9.0, 9.04, 9.1, 9.2.1, 9.2.1, OS X 10.0, 10.1 or 10.2, or maybe 10.3 as far as boot CDs go. OS X will be very slow with 64MB, but at least it'll allow you to see if the machine boots and if the hard drive is good.

Btw, that 512k is the backside cache, not the RAM.