You can usually download the latest firmware from MicroChip, I can only see the PicStart Plus there on a quick look - is your's the old one, or actually a Plus?.
If you have an old Picstart Plus using a PIC17C44 chip, you need at least firmware version 3.00 to program a PIC18F452. That is according to the READ.PLS file that comes with MPLAB v5.7. The required hex file for firmware ver 3.00 is also bundled with MPLAB v5.7.
Here is a portion of the PICSTART help file (also with MPLAB v5.7) on the required items to upgrade your PICSTART:
Required Equipment
Operating PICSTART Plus programmer with MPLAB IDE software
Blank/Erased PIC17C44 microcontroller (25 MHz or faster)
Upgrade hex file (psf#####.hex, where ##### is the version number), found in the MPLAB IDE install directory
Phillips head screwdriver