I've noticed that a lot of people have been posting questions on a heap of forums asking how to transfer and use GPSP saves on a computer emulator (VisualBoy Advance) and still be able to use them on GPSP. After a lot of trial and error, I've found a way to do this.
1) Copy the .sav and .svs files from the GPSP folder into a backup folder.
2) Open VisualBoy Advance and go File/Import/Battery File and choose the .sav file.
3) Do what you want to do on VisualBoy Advance and save the file as a VisualBoy Advance Save File (.sgm).
4) On VisualBoy Advance go File/Export/Battery File and save it as exactly the same name of the ROM that the save file is from.
5) Rename the VisualBoy Advance .sgm file to the same name as the ROM file, the slot you want it to be in and then .svs as the file extension. e.g. Need for Speed Carbon: Own the City0.svs.
6) Copy both files back to where you copied the files from originally and run GPSP.
7) Go to the slot you put in the filename. There should be some random picture there. DON'T WORRY. This is perfectly normal. Just load the file and everything should work perfectly. If this doesn't work try to load savestate from file under savestate options.