I used Moborobo and superoneclick to root my n90, http://www.moborobo.com/ give it a go!
I can confirm that this method works for rooting the device.
The instructions are VERY simple.
1) Link: Download Moborobo
2) Download this modified SuperOneClick - Short Fuse
4) Make sure USB Debugging is enabled on your tablet (Settings --> Developer Options)
5) Connect your Window N90 Dual Core tablet to your PC
6) Wait for Moborobo to see the device
7) Extract the contents of SuperOneClick
9) Click on Root
10) Click on Yes (it says device is already rooted do you wish to continue)
That's it... you are all done and ROOTED!
Edited by MrTasselhof, 20 June 2012 - 08:23 AM.