A question about some old DRAM

My friend wanted to upgrade his memory in his old HP from 64 to 190 to get by while he saves for a newer system. The HP has an 810 chipset of some sort and has 64 meg of PC100 installed. Since PC133 is easier to come by and cheaper, I thought I would just get some of that... After all it's the same stuff that's just able to run a little faster. Needless to say, it didn't work. Now I'm left wondering if it's incompatability or a bad stick of RAM.

Any ideas?

In some situations, PC133 won't work. It happens more often in setups like HPs and Dells. See if you can get some PC100...that's the only way to know for sure, I think.

Did you try the 133 stick by itself? And in each mem slot? Also did you check BIOS settings? You may have to set mem to 133 or by spd.
Just a few thoughts...