iPod touch Lost memory

I did a quick search but couldn't find a thread that answered my question. Sorry if this has being answered in the past.

I have an iPod 2G 8Gb. I had it jailbreaked for about a year, in which time I installed software that I used. Some time ago, I decided to update the OS to 4.2.1, fully aware that I would need to wait till a jailbreak was available. So, I restore the OS and did the upgrade.

The problem is that now, the iPod only recognizes a capacity of 6.8 Gb. Somewhere in the process, I lost 1.2 Gb of memory.

How can I recover the lost memory? Thanks in advanced.