Hello Im tring to put together a computer for my kid with all my older computer parts. Now I have a 450w p.s. and a socket A/Anthlon 1000+ mobo and CPU. My problem is it keeps freezing up at random points . At first I THOUGHT it was the ram I had a 256 ddr266 and a 256 ddr333, so I tried just one DIDNT help. then I found a second 256 ddr266, with both matching chips in it seemed to run longer but in the end it still crashed :-?. Does this even matter, or should I be looking somewhere ELSE like a software issue? The specs on the board say it can handle both but I have never ran two different speeds before. I have a agp card comming maybe that will help?

Giga-byte mobo
Socket A AMD Anthlon 1000+
2x 256 ddr266 kingston memory
maxtor 120g hdd
thermaltake 450w p.s.
liteon cdrw
Did you reinstall Windows from scratch?

You can test the RAM (1 stick at a time, then both together) with a free download at www.memtest86.com to find out if that is the issue, as well as check on the www.crucial.com site to see what RAM and characteristics you should be using with that motherboard.yes this is a fresh install and is all updated. I have gone through the "compatible" ram list, but is it alright to mix different speeds of RAM?Mixing and matching ability depends on the motherboard. Some will HAPPILY accept anything you throw at them whilst others will bork if the manufacture batch is different. In general, the older the board, the less likely you are to have a problem.
Gigabyte support is pretty good and, as GX1_Man has said, use Crucial or Kingston as a guide.