How to root-Dell Streak 7 to Jellybean 4.2
In this video I go through the steps needed to flash a Dell Streak 7 up to the latest Jellybean (4.2). This process makes use of the the CM10.1 flash kit here
http://forum.xda-developers.com/showthread.php?t=2130081
Everything you need is in this thread and the zip file itself. JB gapps is linked in the thread and the zip file contains the drivers needed for your PC to talk to the APX mode (Nvidia flash mode) of the Streak 7. To go into APX mode power the streak off. Then boot it up by holding power, vol up and vol down. You will know you've done it by the hardware buttons lighting up white. Then connect it to your PC. You will likely see an unknown device in your device manager. Just go into it, tell it to update the drivers and point it to the drivers in the folder you get from extracting the zip. If you want to back up your streak before hand, get TWRP here - http://forum.xda-developers.com/showthread.php?t=1659546
This thread also contains drivers you might want if you don't want to get it from the CM10.1 flasher - http://forum.xda-developers.com/showthread.php?t=1484406