Quote from nononsense:
With a tool like PartitionMagic or Acronis Disk Manager you can do this.
Even under the active - OS, you can (re-)partition your OS drive any way you want.
Except if you want to modify your partition holding the OS itself. Here you can only enlarge it provided you have the free space to do this.
If you would manage to run the partitioning tool from another OS - self booting CD or floppy - you could do anything you want, provided you are prepared to adapt your boot control file (for XP: boot.ini) as required. This is a bit more delicate though.
Note that deleting or creating non-OS partitions 'ahead' of your OS partition may also require adaptation of your boot file.
If you are not sure about all this, better don't try without adequate backups!
nononsense