|When you remove/replace the CMOS battery, nothing gets "erased", but the BIOS settings do return to their factory defaults. One or more of these default settings may be inappropriate for your current PC configuration, therefore not allowing it to boot.|
Go into BIOS Setup and check these settings, change as necessary:
First Boot Device - make sure it's set to "Hard Drive"
SATA Mode - may need changing to the other mode from what it is now.
Don't forget to save any changes with "save to CMOS and exit" (usually by pressing F10).