On booting W98, sometimes the picture of windows goes fuzzy (flashes on/off) as boot is taking place, and the computer will not boot. Also, once booted fully, the computer sometimes crashes for no aparrent reason.
My hard disk was 90% full, so yesterday I reduced the data from 140gig to 90gig, but today I a getting the same problems.
Please post your system specs.
98 is going to have problems running on partitions larger than about 128 gig. You say the drive was 90% full with 140 gig of data so unless that's spread out over more than one partition that's probably at least part of the problem.