Dude,
Dividing programs and data is a personal choice. I partition mine to be 8192 for the C drive for OS and apps leaving me about half the drive to spare (no pagefile).
This allows me to move the nasty old My Documents, My Pictures, My Music and Favo(u)rites to my Data drive.
I also make a Restore partition and do a clean image for restore purposes. My Data drives vary between machines.
To answer your question (and I agree about the previous comment about bad performance) the drive is not very quick. Just to load the OS and that's it.
SATA II drives (especially the new 74 GB Raptors) kick serious donkey and leave the old SCSI disks in the dust.
In short, invest in a new SATA II drive. The added hassle of adding a SCSI card, changing the boot order etc. is not worth the 9 gigs.
I don't mix SCSI and PATA/SATA on machines. Easier to manage. My main server is all SCSI with a 9.1 GB boot disk and 2 x 74 GB SCSI disks. My backup server is PATA.
Hope this helps.
