More Dimension Issues

Hello,

I have recently acquired a Dell Dimension 4500 Desktop PC
while tinkering with it i installed an 80GB Seagate HDD but for reasons computer just beeps at me (it beeps 3 times then goes on making normal Computer noises),
i don't know why it does so, i looked inside the case everything looked OK from what i saw.
Also I'm not getting a connection from the PC to the Monitor everything is running fine but why no connection i checked the VGA cable and the power cable to make sure they were not loose and the weren't.

Here's some specs if you are interested:

Pentium 4 Non Hyper-Threaded (Unsure of the GHz)

1GB of DDR2? RAM

80GB HDD (Don't know if it's dead)

This is what i can remember off the top of my head

Thanks,

Ninja