I am guessing that by changing the CMOS battery the BIOS settings changed to default. Check the BIOS setting for SATA. If it is AHCI try changing it to Legacy. And if Legacy try AHCI. F2 at boot can access the BIOS settings.
Got message saying battery low, so I changed it.  Now Windows won't open (in any mode). I get the first screen (Windows XP) then I get the "we apologize for the inconvenience...." screen.  If I hit F12 (Boot Options), I get the following options to look at : SATA0-WDC WD800JD-75MSA2 On-board or USB CD-ROM Drive   System Setup Diagnostics Intel (R) Management Engine BIOS Extension (MEBx)   From here on in, I'm clueless.  
Changed CMOS battery now Windows won't open (Optiplex 760)