There have been many requests for a method to convert or use the external microSD card memory as internal SDcard memory. XDA forum member trip007in has discovered a hack courtesy of 3snow at www.lowyat.net and has posted this in the forums for other members to try.
The hack swaps internal and external memory in order for games to make use of the larger space and for Maps for Navigation. It makes use of a modified vold.fstab file which replaces the original and swaps the memory.
The XDA member has tested the hack on the i9003 which requires root access.
For more information and to download the modified file, head on over to the modification thread.