You should always split up a drive if you can. Anything over 10 gigs can and should be split up. Because it's not a matter of if you will reinstall Windows, but a matter of when. For the 15 giger, do a 10 gig System partition and the remaining for your files, etc. If you want performance, get 2 or more drives and then split up the swap file and put the swap file and temp files on the same physical drive. I have my swap file spanning 2 drives, almost in a RAID type configuration.
Take it from a system admin.
The Yellow PS2 auto-boots all. PS2, PS1 stealth and DVD movies.