Optiplex GX60 processor options

Hi,

I've got an aging GX60 with a Celeron 2.4 processor, in an 845 chipset motherboard.

To avoid the pain of getting a new machine, software licenses etc and recreating everything from scratch, it would be good if I could just replace with a better processor, but can't find any information anywhere as to what this would support.  I have the service tag available if that helps anyone.  Cheers.