Hey, this is a pretty easy and simple process. I assume you are just locked out with a password lock, here is how to restore it.
you need android SDK (self development kit) just google android SDK to download install it to C:\ (assuming you are using windows, dont know how to do it any other way) now once installed open up SDK manager and download android SDK platform tools and android 2.1 SDK platform.
once done that download a thing called superoneclick. just google shortfust and download from there
Now if using windows 7 go to computer click system properties and advanced system settings. once there you need to click environmental variables in the box that pops up you need to go to the second section where it says system variables and look for PATH in the text box. then change the path of PATH to C:\android-sdk\platform-tools\adb.exe
(assuming you installed in C:\, if not change the path to where ever it is).
with windows XP just click start RIGHT click my computer properties and find environmental variables and complete the same steps as windows 7 instructions
now turn on your device and plug in your USB cable. once done that open up the superoneclick and extract it to a folder on your desktop, then open the application and click SHELL ROOT, a few prompts saying auto version verify didnt work just click yes.
now once it has finished it may crash it still should have worked though.
Now open up your command prompt
(windows 7 & vista) start then type cmd in search and press enter
(windows XP) press start click run and type in CMD
now once in CMD a black box should appear (sorry if you know what CMD is just to make it clearer) type in the box "adb shell" without the quotation marks
wait for it to finish
once finished it should pop up with a # or $ sign
If its a # sign your on the right track
if $ sign go back to the super one click and re-do that
so if you have the # sign just type "wipe data" without quotes and it should re-boot your device in factory default mode