The IBM 75GXP dying is no surprise - they've been having QC problems for quite some time now. Maxtor used to be garbage in terms of reliability, but supposedly they have improved that rating in the last 2 years or so. I haven't had any Maxtors manufacted after 2000 that died on me. Doubt it's a fluke, considering both Maxtors.
Check IDE cable, maybe you're using a rounded cable and some of the insulation is peeling off? There could be cross-over frequency interference.
Check the PSU like you said, maybe it's overpumping the ampeage on the 12V rail.
Check placement of the tower, any rotating disc media should be mounted parallel or perpendicular to the tangent level. Maybe yours is slightly out of alignment, and it's wearing down on the spindle.
Maybe your IDE controller is iffy - usually IDE controllers aren't problems because they're had so many years to mature, although sometimes RAID setups have difficulties, normal IDE should be AOK.
Those are the only things I could think of at the moment...good lucky in reviving that 60GB D740X