The acronym ASPI stands for Advanced SCSI Programming Interface. ASPI layer, drivers, interface & file system are synonymous. System software and applications use ASPI not only to interface with SCSI devices but with IDE/ATAPI devices when ripping & burning CDs. The ASPI protocol is primarily based on one file, wnaspi32.dll. There are other files that support wnaspi32.dll, referred to as the ASPI layer. The Windows 95/98/Me install includes wnaspi32.dll & the ASPI layer. The 2K/XP installs do not include neither wnaspi32.dll nor the ASPI layer and instead use the ?SCSI Pass Through? interface. It is better to use the ?SCSI Pass Through? interface the ASPI option is in there just a backup option. If your CD Burner is giving you trouble.