N0b0dy is correct about performance - if you move the paging file for performance, you should move it to another hard disk entirely. Moving it to a separate partition will not improve performance at all (in fact, if the partition is towards the outside of the physical platter(s), it can actually be slower). If you're looking simply to reduce fragmentation, turn the paging file off, defragment the drive, then turn it back on to a fixed size.
As to keeping the paging file clean, you can
set the paging file to be cleared by Windows itself when you shut down or reboot the machine, which should achieve similar results.