[arish_06]

hmmmm...the memory decrease seems pretty weird.
Just roughly how many times have you formatted your player if you have since you purchased it?

If you used a firmware from s1mp3.org, which one did you use? Maybe the firmware's taking up some memory. Check the size of that firmware? ...well it shouldn't be upto 100MB so I am pretty sure that's not the problem.

Maybe the firmware you're using is designed for 128MB player so it is reporting back memory around 100MB.

Are you talking about the dump firmware that was giving you trouble before?
If yes, then upgrading your player with that won't help because it may put it back to recover state.

For now, keep trying with similar firmwares and see if you can find one that fixes the problem.