Adaptec's ASPI is written for Adaptec products. Microsoft licenced ASPI for Win9x but along the way they got into a fight and Microsoft did not include updates in the software. This nonsense continues as WinXP with its SCSI Passthrough Interface (SPTI) written by that wretched mob themselves.
While the Win9x licencing issue bubbled along, Adaptec restricted the ASPI d/l to computers with an Adaptec product installed. After MS wrote and disributed their SPTI, Adaptec then made their ASPI d/l freely available again. The only reason one needs to use ForceASPI is to go back to 4.60. All the warnings on the Adaptec site are 'licencing'-related nonsense, designed to scare the casual observer away.
The main issue with ASPI is installing it if you don't have an Adaptec product. I think the only software application that needs it now is DiscDump. burnatonce is now over it and so are many other apps. Don't install it if you don't need it! By itself it does nothing, except introduce potential instability issues.
Win95 was basically a GIU for DOS are there are deeper issues related to SCSI products than just ASPI version numbers.
The 4.7x versions were written for WinXP are designed quite differently from 4.57 and 4.60. For some reason 4.60 is perfect for XP if you need it for 3rd party software but don't have an Adaptec product! We have a mission-critical mini-LAN at work with Adaptec SCSI Ultra320 cards and XP Pro. v-4.7x sucked so hard we resorted to ForceASPI for v-4.60 and couldn't be happier.
If you checkout the ASPI links in the CloneCD Down & Dirty thread, the full messy story is available.