Can anyone tell me what a BIOS upgrade on my computer means (simply) and how much it would cost to get one?

Bios upgrades are free and usually prety simple to perform. Just find the manufacturer and model number of your motherboard. Goto that companies website and look under downloads for the latest Bios version. Download to a floppy or CD and boot your PC from this disk and the PC will do all the work. ****WARNING**** Do not mess with the PC while it is updating or you could erase your BIOS. If that happens then you will be hurting in the pocket book.