There are other ways to get mass storage card access than converting to another compiler with all the fun and trauma that entails. I have just used the Vinculum VDIP1 with a PIC 18F4620 project. The VDIP1 takes serial data from the PIC and drives the USB interface. The VDIP1 handles the FAT 12, FAT 16 and FAT32. By using a common USB to CF, MMC, SD, etc, card reader you get read and write access to most memory formats.

In my application I log data from a scientific instrument to a USB stick. I am using the default 9600 bps async uart writing to a 1 GB USB memory stick.

I have posted the code under the Code Examples section.

Cheers
Brian