that's exactly what I have my partition set up as!
C: = 10 GB
I have XP Home Edition SP2, Office 2007 Beta 2, Adobe Photoshop CS2, Adobe Audition 2.0, and many useful utilities like Ad-Aware, Spybot, etc.
10 GB is more than enough!
worst comes to worse if you ever needed more space you can always move your paging file from C: to another partition, and that way you free around another GB or so of space.
But 10 GB is more than enough