128MB RAM could also set it back for cache reasons. I know RAM had been aggressively marketed in the late 90s to be the end-all speed booster (having seen 64MB OEM P75's myself in the wild in the early 2000s). Try reducing it to 64MB or 32MB if you can.
Also Redneck Rampage really demands to be played in 640x480 as a MINIMUM due to all of the hi-res artwork Xatrix did (the detailed text looks horrendous on 320x200). SETUP will audibly swear at you about going less than that, and that means something more of a p166+ class to handle it. It isn't typical build engine fare.
and finally, since 10gb's involved, it's most likely FAT32, and for that, smartdrv loading's very important for build engine games (if you're running under DOS). Build has some funny behavior with regards to disk cache and file systems...