Is that all it says is just: "BIOS ROM Checksum error"? There's no additional writing on the screen like:
BIOS ROM Checksum error
Detecting Floppy drive A media
INSERT SYSTEM DISK AND PRESS ENTER
If it says something like "BIOS ROM Checksum error", it's serious. ROM= Read Only Memory ... that's the part which isn't changed by the setup routines, or by auto configuration. There is a checksum stored with it. (All BIOS extensions, like those in the ROMs in video cards etc use the same system).
The BIOS configuration data are stored in battery backed "RAM" (read/write memory), and a new checksum is calculated and written into it when you use the Save and Exit option. Any error message when the checksum doesn't agree with the data will not mention "ROM".
Has it always done this or is it a new problem that recently developed? Have you made any hardware changes in the machine like install a faster cpu or install a larger hard drive? And most importantly, have you attempted to update the bios before now by using a boot floppy disk?
Have you tried installing a new cmos battery to see if that fixes the problem?
You might want to read the info on this page: http://www.pcguide.com/ts/x/sys/booterrGBER53-c.html
It won't hurt to try to update the bios providing you haven't already. After all, what do you have to loose?