Well what kind of ipod do you have?
1. Go to settings
2. pick general
3. pick about
4. then go to Model and check if the first 2 letters are MB if they are not you got to wait for a jailbreak.
Now you got to check what firmware you got
1. go to settings
2. pick general
3. pick about
4. check if you have version 3.1.2
5. if you do go to blackra1n.com and download it {this video will show you how to use blackra1n}
http://www.youtube.com/watch?v=u7DnqOS1njU
if you are 3.1.3 go to http://www.felixbruns.de/iPod/firmware/ and download the 3.1.2 firmware for the ipod touch what ever generation you have
now put that firmware on your desktop and open itunes then click on your ipod and where it says restore hold shift and click restore then find your 3.1.2 firmware and click ok now you wait like 20 minutes. when its done do blackra1n.
if you have mc as your first 2 Digits on model then it wont work it will brick your ipod dont do it they dont have a jailbreak for that sorry
Oh yeah every time you plug itunes in it will say it cant read your firmware do you want to restore dont do that it will take the jailbreak away and all of the data including free apps
it really does not matter on how much memory but what generation and what king of firmware