I would go ahead, and try replacing the battery ($2-3).
I would then, perform a virus scan. There may be a BIOS virus on the drive.
As to a new BIOS chip, you have 4 choices;
1. BIOS update from Patriot, and flash the BIOS.
2. Purchase a programmed chip from Patriot.
3. Purchase a custom programmed BIOS from Unicore software. (around $100!!)
4. If you have access to a memory programmer, you can purchase a chip, and program the code in from the BIOS download.
As I said, I suspect a virus. However, if the battery fixes the BIOS settings problem, your next step may need to be wipeing the hard drive, and starting over.
If the startup files all look okay, you may have a corrupt system file, driver, or registry key.
Chas