I remember artists talking about mixing albums on Macs back in the 90's, but I doubt that PCs were to that level yet. 
 
It took a while before the drivers technology from Windows NT became mainstream in the consumer PC, allowing for stable real-time audio.  Windows 2000, and then Windows XP, built on NT which allowed the Windows platform to expand as a legitimate multimedia platform.  But the DOS based Windows prior to that just couldn't cut it.
 
I messed with some MIDI sequencing on Win 95/98, but that was about the extent of it... keeping audio outboard...