CONVERT A 512 MB duo/produo/MMC CARD TO 640 MB
I guess it works for duo/produo/mmc cards.
PrinCiple:--Your files in duo/produo/MMC is stored in multiple (disk) blocks.So if you format using 16K block, the space used will be 16K eventhough your file is just 1K.If you buy DUO/PRO-DUO, it is usually preformatted with 16K block. Therefore a lot of space is wasted as most installed program files are usually less than 2K.

ProCeDure:--You will need a card reader to do this:-edit:u can also do it by connecting u r phone via usb
1. Connect card reader and copy all your files in the memory card to computer disk.(Make sure you set the show all/hidden/os files to "on")2. Do a format of the memory card using command line "format" and use the /A=size option.Alternative, you can use the Disk Management in Adminstrative Tools to format.Make sure you select FAT16. For 256MB memory card, smallest block you can use is 4K, 128MB is 2K, 64Mb is 1K and 32MB is 512B.
(Note: You cannot use the phone "format ext.mem" to do this as the format just clear the allocation table and does not change the block size)
3. Copy back all files to memory card.
Now you will find that you will have more space.I have installed many software to to my 256MB memory card and it is nearly full. After doing above, I got an "extra" 32MB.
For those who have problem with command line format::
Just use the Disk Managament to format
1. Goto Start->control Panel->Administrative Tools->Computer management->Disk management2. Select your memory card/usb drive. Right-click and select "Format"3. Select "FAT". Choose Allocation size. For 256Mb MMC select 4K, 128Mb MMC select 2K, 64Mb MMC select 1K and 32Mb MMC select 512B