|The bios defaults are loaded when the Cmos battery is too weak or dead (or if it's installed backwards - the + on the battery should be visible when the battery is installed - or if the battery has a poor connection to it's socket, e.g. the socket is corroded, or if one contact on the battery socket is bent and is not touching the battery).|
02B0: Diskette drive A error"
The default in many desktop bioses is for one floppy drive to be enabled; if you're not using one, you may get that error while booting if there is no floppy drive. You must go into the bios Setup and set that to disabled, as well as set the date and time, when your Cmos battery is too weak, or the first time you boot after you have replaced the Cmos battery, then you shouldn't get that error as long as the computer is still running when the battery is too weak (you can Restart the computer and the bios settings will be retained), or after that when you boot after having replaced the battery.
However, you may have something else wrong as well. When you press F2 the computer should boot into Windows, unless you have more than one hard drive, or more than one partition on a single hard drive, and the default Boot Order or similar settings in the bios do not select a bootable drive, or a bootable partition, in which case you must change the Boot Order settings too so you're booting from something that is bootable.
If the Boot Order or similar settings are right, and you do have something bootable, if Windows still won't load, there's something wrong with the hard drive and/or the data on the bootable partition that is preventing Windows from loading.
Check your hard drive with the manufacturer's diagnostics.
See the latter part of response 1 in this:
(thanks to Dan Penny for this link:)
Hard Drive Diagnostics Tools and Utilities
If you don't have a floppy drive, you can get a CD image diagnostic utility from most hard drive manufacturer's web sites, but obviously you would need to make a burned CD, preferably a CD-R for best compatibility, on another computer if you need to.
If the hard drive itself tests okay, any data problems found can be fixed, one way or another.