Connect the Nexus 7 and tap on Settings-About Tablet-Build version 7 times.!
This will install basic driver for windows
Now, tap on connected as media device(MTP) icon, but you will need to change it as Camera device then
Go to device manager on windows, select Nexus 7 and then update the drivers using the driver avaliable on this link http://developer.android.com/sdk/win-usb.html - This will install a driver ( You can use it with this one)
Now tap on Connected as Camera device and change it to media device - This will install one more driver and you are ready to go.!