Right.
How old is old? Is it an IDE or SATA drive? If it’s SATA, go into BIOS and look to either enable IDE compatibility mode or disable AHCI (it’s the same thing, worded differently).
Again in BIOS, see if there’s any ‘boot sector protection’ or ‘virus protection’ enabled and disable it if so.
See if you’ve an option to “reset configuration data” or “reset ESCD” in BIOS and select it. (this is a one-shot deal and will change back after you reboot, this is normal).
Look on the website for the manufacturer of your motherboard, see if there’s an updated BIOS available.
+1 for ‘try another CD’ – download Ubuntu again, seems to be the common denominator here. Perhaps try a different version.
It’s been a while, but are you forced to go for ext4 partitions? Try using ext3 instead?
Did it work back when you had Windows on it?
+1 also for PenDriveLinux – I use this a lot at the moment, I’ve got a heavily customised UBCD on a stick along with a LiveCD (persistent) Ubuntu install and various rescue tools. It’s fantastic.