I'm having the same issue with a Dell Dimension 2400, same warning. The OS (XP Home) has been reinstalled once, using the recovery partition, & despite the fact that I increased the RAM from 768MB to 2GB, it runs no faster (that is, when it's running).
I've been told that part of the issue (the slowness) is due to the 2.4GHz Celeron CPU, I intend on replacing it with a compatible Pentium ($10 on eBay). But I need to get this BIOS issue fixed before spending more money on it.
At first, I thought it was the factory keyboard (has a blue/purple connector), as there was a warning about no keyboard detected, but a USB one didn't change anything. 40GB IDE HDD has been cloned to a known working one of 80GB.
If I can get this BIOS issue right, then I can hopefully get the OS right, or make a Linux PC out of it.
Cat