Deleting the 2x 4x 16x etc. from root of hard drive?

Is it ok to delete the folders 2x, 4x, 16x, 32x etc.. from the root of my harddrive? I'm trying to make a map for California but my harddrive keeps running out of space because of those folders! :( They already have those folders in the gmdl/bin/debug/_California. Please help. When I right click on the 2x folder and go to Properties it says
Size - 352mb
Size on disk - 15.9GB!?
What's up with that?

Thanks :)

you probably storing the map on the old FAT filesystem... use FAT32 or NTFS to save space..

Oh, I'm using my External Harddrive and it's using FAT32. Should I use my regular hard drive (Local Drive (C: )? It only has 5GB Freespace left. Will that be enough for downloading California? My Local Drive (C: ) is NTFS BTW.