Upgrading memory on a computer using ME..

[Powerstroke2000]

The other day I upgraded the memory (DDR) in a friends computer that runs with Windows ME, with an unusual issue.
After installing the memory (this is on a P4 machine) with a 512 addition to it's 256 megs what it currently had, the computer would boot up, going through it's boot process, showing the 768 MB of Ram, but would NOT go beyond the first few screens, in which it would then just freeze up. Numerous reboots would not alleviate these issues!

So, we ended up running out of time, just figuring there was a "coincidence" of issues, as my friend has had continual problems with ME, and my suggestion was to eventually bit the bullet and upgrade to XP.
As it turns out, he retried again and again to reboot (fingers crossed with hope) that the computer would eventually boot up, but no luck. So, he then pulled out the new Ram I installed, and OF COURSE, the computer then booted up, albeit with it's previous issues, but at least it is useable.

I now wonder...does the computer have to have similar Ram sizes in order for it to boot up?
Can you not add a 512 to a 256 chip on some motherboards? It does have 4 slots for Ram.

Any advice on this, and how to get ME working like a champ would certainly be appreciated...or even advice to upgrade to XP if that is the best choice?

Thanks..

PS2000

[glc]

What is the motherboard model, or if this is a name brand computer, brand and model? What is the brand and specs on the ram you tried to use and the existing module? Will it run if you pull the 256 and try it with only the 512? Did you run ram diagnostics on both modules?