My nephew attempted to replace a RAM stick only to find his PC wouldn't work. He re-inserted the old one and now the PC is dead, apart from emitting continuous long beeps. I can't get over to assess the damage for a few days, so any suggestions here would be welcome. I can't give you any details about the PC, but I think the OS is Windows ME.
Did he use an anti-static wrist strap or hold the PC's chassis while installing the RAM? When someone walks across a carpet they generate around 30,000 (or 3,000 - I can't remember off the top of my head) volts of static electricity. We don't feel it yet 30 volts is enough to damage/kill a PC component that has microchips on. I looked up my notes and if the BIOS chip is an 'Award BIOS' then continuous beeps indicates that the PC has bad memory.
That was my first question to him and he says he earthed himself on the case of the PC before surgery. I'll bet it wrongly seated RAM or an accidently disconnected cable. It's the long beeps that confuse me as they usually indicate a PSU or keyboard problem.
Also check the graphics card is seated correctly(if it's got one)- sometimes the connectors can move when RAM modules are fitted - long beeps can be due to no video. Check any other PCI cards too e.g. modem, sound card.