What OSes? But the more partitions the better! It's not the size that counts, its how you use it. It's not the size that counts(but not too extreme) and it's not how you use it!! It's how you say you use it!!! .... Wha? I got 6 partitions on this current machine. One for Windows XP Pro One for Linux (Which I barely use because the free version of RH9 is discontinued) One for Windows 2000 One for Windows 98 :S The apps partition (lazy ass mofo who doesn't like reinstalling certain software, also dual layers for both my XP/2k to Win98) The big 120GB HDD for my downloads/pictures/movies. The matter is, if you use XP as a default, your PC will run better using NTFS partitioned drives insted of the FAT32 format.