That doesn't sound good - you've probably got both hard drives 'active' if you can simply swap the boot order in the BIOS without a boot manager. There should only ever be one 'active' partition in a computer across all hard drives. Otherwise, you can expect to get data loss because having more than one active partition confuses some versions of Windows if you keep swapping OS like that.

Chances are that the FAT tables on the disk aren't updating properly because of this - you change something, but when you reboot into the other OS, it chages it back from a (older) copy of the FAT because it thinks something is wrong.

First go into the BIOS, choose the disk you want to boot from e.g. Win98, then boot into that OS. Then run FDISK, and 'set active' that same OS's partition - this will disable the other OS and this problem shouldn't happen. If you want to dual-boot between WinME and Win98, you need a boot manager of some sort (e.g. BootMagic), it changes the active partition and disables the other on the fly when you boot up to avoid this sort of conflict in the FAT tables.

Of course, there <I>is</I> a possiblity of a virus, but if you've got the latest version of Norton, it should have been detected - there doesn't seem to be any recent viruses on anti-virus web pages which cause that problem.


PS Stick with Win98