[size=12]Hello,  I have a HP with intel celeron, 801mhz, currently 2 - 128 pc133 ram cards installed.  I ordered 2 256 for a total of 512, when I removed the 2-128's and installed the 2-256, the computer would not even start, no hp logo on monitor, nothing.  I then put back in 1 128 and left the 2ND 256 in, this time it started with the hp logo, but nothing else.  I then went into bios and it only showed the 128 and NO hard drive listed only my dvd drive.  I reinstalled both 128's and computer back to normal.  The 256's are kingston pc100 3.3V SDram.  

Did I not purchase the correct thing? or might there be another problem?

Thanks for any help![/size]The RAM sticks are probably not COMPATIBLE with your motherboard. Also, the ones you purchased are PC-133 right?Try here:

Crucial.com

Match your computer with their RAM.  You'll be sure to get the right stuff.

Alan <><  medieval30, did you use Kingston's Memory SEARCH?  Did you find your computer listed?The kingston was pc100, Lesson LEARNED and I will check that site to see what is compatable.  Thanks for the answers!No problem. Happy to help .