I have an ASUS EEE PC 1011PX with Ubuntu Linux Desktop Edition v 10.10. I want to revert its state before its first start where a wizard came up and asked things username, passwords, etc... I hope there is a command or something to revert everything back to the first start.
The wizard you mentioned is only available from a fresh install - it is part of the installation routine.
If you want to reset your desktop then there is a great answer describing this.
An alternative would be just to create a new user account and copy the files from one account to the other.
10.10 is almost out of support (April 2011) - so you perhaps should consider upgrading.
Obviously 12.04 will be available at that time - full instructions on how to install from USB is available from ubuntu.com.
Unlike 10.10 - there is not a specific version of ubuntu for netbooks. The netbook design has been combined into the one Unity interface (hence its name). For netbooks, my recommendation would be to use the Unity-2D interface since it is much lighter for the lower cpu-powered netbook.