2nd stick of PC2100 causing continous reboot?

I've been upgrading my sisters pc and have found that when I install a second stick of PC2100 into her K7S6A motherboard the pc will go into a continous reboot.
The PC2100 is a generic brand, but both sticks do work if only one is installed in the motherboard at a time. Are there any settings that I could mess with to try and get this second stick of PC2100 working? According to the motherboard manual the board will support up to 1.5GB of PC2100 so I know I'm ok there.

Any ideas?

your motherboard is prolly real old and hasnt used more then 1 stick in so long that its saying what the hell why start now....

Actually the motherboard is only 18 months old so I can't imagine it would be that.
Any other suggestions?

Could really use some ideas here if anyone has them.

lol guess my idea is best for now

I appreciate the thought, but I really don't think that's it. If I use two 512 sticks it does post and goes to the "Windows loading" screen, then just reboots and repeats the process.

I did use one 512 and one 256mb stick and it actually started into Windows, so that's a good sign but still not the 2x512 I'm aiming to get to.

I'm thinking it's probably just a BIOS setting that needs to be changed in order to get this working correctly. I just want to see what others think before I go messing around too much.