With the price of a small (<10 Gb) hard drive now under $25, why not
make a dual boot system by adding a drive and installing one system
(XP or 2000) on one drive and the other system (98 or 95) the other.
To eliminate any possibility of conflict, just turn off the drive not
running the computer at the moment. There'd probably even be room for
a Linux partition of you'd like to go for a three-way!
I never thought I'd live long enough to hear people be nostalgic for
Win98! (Probably what my grandmother thought when she saw that wind-up
phonograph in my living room.) I've found the most recent Win2000 to be
quite stable and XP almost as good, running for 30-40 days between
reboots. 8 hours on Win98 would have been a record for me.