One point I'd like to add... if you are concerned about your hard drive data, make sure you aren't booting with a manufacturer's "system restore disk" as this WILL typically wipe out everything. This will likely be a CD, though, as a floppy wouldn't have enough space to restore the system.
I've seen people lament the loss of data because they put in their Gateway System Restore CD. And I'm sure other companies send these things out with systems.
But an ordinary floppy boot disk will do just fine. If you don't have one, find a friend to make one. Not sure exactly where to go in other operating systems, but in Windows 98 you can make a boot disk in the Add/Remove Programs area, under the Startup Disk tab.
Also, if your CMOS battery is dead, and you happen to have one of those motherboards that it is not removable on, you may be able to pick up a small lithium battery pack, and your motherboard will likely have a 4-pin connector for it. I've seen some old Compaqs that are like this.
Hope this helps,
Jason H.