I bought my PC a few years ago (a few days after XP was released) and it's never run very smoothly, there seemed to be a minor problem every few days. Just today, it's refusing to boot up at all.
Just for reference, I've changed the CDR drive once, added a slave HDD and upgraded from 256MB to 1GB RAM. Just a few months ago, my master HDD died and I replaced it, but that's where my boot up problems really started. (I'm pretty sure I haven't touched anything else - I wouldn't dare!)
Right after I'd replaced the HDD, my PC refused to boot up, but I (somehow!) worked out that pressing the eject button on the DVD drive would give it a kick and make it boot. After a few days, I didn't need to do anything like that, but instead, it would reboot itself a few times before starting up Windows properly. It would do the normal beeping (2 beeps separated by a pause), and after the second beep it would reboot and go back to the start of the sequence. Sometimes, it would reach the "Welcome" screen for XP, and then it'd reboot again. Sometimes, it wouldn't boot at all (no beeps), but after turning it off at the mains and leaving it for a while, it'd work again.
But today, it's not beeping and my monitor is receiving no signal, although the fan is working. I'd left it for a while, tried again several times, and it's still not working. I also tried using a different PSU, and it still wouldn't boot up (I know the PSU I tried works, because I'm using it on this PC that I'm using right now). I tried disconnecting all drives and cards, but it still wouldn't boot.
Does anyone have any ideas what's wrong?
(could I just emphasize the point that this PC was not built from scratch by me)