My PC - 750GB (Unformatted Capacity)
Server - 4.2TB w/ 544GB free (Windows Home Server - 8 various HD's in it from 300GB-1TB)
Wife's PC - 500GB
Son's PC - 500GB
Media Centre - 300GB
3 Laptops - 440GB
"Spare" PC's - Probably in the 6-800GB total region
All in all - too damned much considering my first PC had a 2GB hard disk and that was "HUGE" because most PC's "only" came with 1.2....