I recently added an extra 2GB RAM and an updated video card to my system. It runs OK afterwards, except when it boots up. When I hit the power switch, all the fans run at full speed for ~10s, then slow down, and then there is a distinct 'ticking' noise every 2s for another 10s or so, then the HP BIOS splash screen appears and it boots up more or less as it always did from that point.
The other funny thing is I cannot access the BIOS -holding down F10 through all of this doesn't do anything.
I'd guess that system is trying to initialize but then something is faulting out due to a conflict or some other reason. Then it resets itself and loads up with different parameters.
You need to get in that BIOS. I would try to do a CMOS reset by either using the jumper or removing and reinstalling the battery. Hopefully it'll let you in. Also, try other buttons, like F1 or DEL for example.
Ticking noise is a concern. Try to determine if it's coming out of your hard drive. I hope it's not
When you get into BIOS, load set up defaults and save. See if it's still doing it. If it is, pull out your MoBo manual (or download it) and start reading. Maybe something isn't configured right. You can try removing new memory and then putting old video card back in to see if it would make a difference. If you still got nowhere, then I'd start stripping your hardware one at a time while attempting to turn on the system after each try. (I'd start with that SCSI card - never liked those things anyways)
Screen shots of your BIOS screens could be helpful if you're still stuck