i tried upgrading my brothers old hewlett packard 8754c pavilion , it has 2 slots and the most it can support is 512mb of ram. so i bought a 256 and i left the 64 it had already, the problem is when i put the 256 in it worked fine, i connected the computer in my room because i have cable internet and i wanted to update my bro's computer , when i was done i disconnected it and plugged it in my bros room. this is where the problem started, i got some sort of error message saying it wasnt reading the memory, i dont know the exact message but somewhere along those lines, so i tried swithing them around(64 and 256) and still didnt work. the computer would boot then freeze, so i just took out the 256 and left the regular 64 it came with and it works again... can anyone help me? why doesnt it want to work anymore?? any help will be appreciated, thanks in advance.