The dimension 2400 does not have sata drives.
Your hard drive is bad or not properly set to cable select.
Try clearing BIOS:
*If battery is more than ~2-3 years old, this would be a good time to install a new one. CR2032 3-volt lithium ion battery, ~$2 at discount stores.
BTW: Microsoft is no longer supporting XP so there won't be any more security updates or hotfixes. If you insist on keeping XP, you should be running SP3, but that won't be updated either.
Forum Member since 2004
I'm not a Dell employee