PC boot problem

I'm not all that tech savvy, so be gentle with me. (I know a bit, but also know that a little knowledge can be a dangerous thing...) Anyway, I'm having a strange problem booting my PC and hope that someone might be able to help me.

I'll start with the basic specs of the system...

ABIT Fatality Mainboard f-i90hd
Intel Core 2 Duo 6420
3 GB RAM DDR2 667 (3 x 1GB sticks)
ATI X1650 Graphics Card
Running Windows XP Pro

It was all working fine, and then I plugged in a new monitor (yes, the system was off at the time). Viewsonic VX924 - apparently it should plug and play no probs at all.

Now when I try to boot the PC, I get stuck on the first boot screen - it's the one where it tells you what processor you've got, then checks your memory, then checks your hard drive, etc and has "Press DEL to enter setup" and a long alphanumeric number (apparently something to do with the bios revision) written at the bottom.

Basically, what happens is that it tells me that I have a main processor - says something like:
Intel Core 2 Duo 2.13GHz (2.66*8.0), 1 CPUs

It would normally next tell me that I've got 3,140,000,000 bytes of memory, but it never gets to that bit - it just hangs there with one line showing me what my main processor is... no beeps or anything.

Now the curious bit is that if I leave the computer for about half an hour (sorry, I wasn't sitting at the screen all that time) it does eventually boot up just fine (I'm writing to you on the PC at the moment).

If I hit DEL while it is hanging, I do eventually get to the setup (again, I have to leave it for about half an hour). Nothing seems to be amiss there though - it can see all 3GHz of the RAM (as can Windows).

Things I've tried:

1. Turning off and on again. Didn't help
2. Using the old monitor. Didn't help
3. Removing the memory modules in turn. Didn't help
4. Opening the CPU case checking it was seated correctly (I bottled out of actually taking it out and putting it back in again). Didn't help

Things I'm wondering...

1. Should it say 1 CPUs on the bit where it's hanging? I have a vague nagging suspicion that it used to say 2 CPUs (the processor is dual core), but I'm not sure. Once I'm into windows, my hardware manager sees two processors and tells me that they're both working correctly)

2. Could it still be a RAM problem? Even though both the BIOS and WinXP seem to see all 3 GB without any problems.

3. Why would changing from one plug & play monitor to another plug and play monitor cause this prroblem?

4. Can anyone help?

I suppose I should count myself lucky that the PC still works at all, but it IS a bit inconvenient having to wait half an hour to boot up...

Thanks in advance

Stuart

remove the battery from the motherboard that backs up the CMOS. Leave it out for 5 minutes, replace battery, boot up pc, enter BIOS and change the settings you need to (you might well get away with the time/date and disk boot order unless there are some specific settings you require for overclocking).

Dear Killie

Thanks for the advice - it worked!

- Stuart

Looks like it's fixed but hanging at that point would lead me to look at my hard disk(s) to see if there is a problem with them.