Nexus 5 not connecting to PC I tried connecting it nexus 5 to my pc via USB. Although it shows as connected in my external devices and also shows up in My Computer, but when I try to open it and don't files to my phone, it just shows a plain, blank screen with the green placing had on top.
Enable USB debugging: Go to phone settings -> About -> Tap build number repeatedly until developer menu is enabled. Go there and tick USB debugging.
On your PC, go to your device manager (You can find it in Control Panel, System) when the Phone is plugged in and set to MTP.  Locate the phone, (it might come up as "Android Phone" if so open the tree a level. On my computer it says "Google Nexus ADB Interface" but it might be different on yours depending on how you've got things configured) right click on it and chose "properties" from the fly out menu. 
Go to the Driver tab
Click Update Driver. . .
Click Browse my Computer for driver software
Click Let my pick from a list of devices on my computer
select USB Composite Device
Close the driver assistant


Your Nexus 5 should now appear as an MTP device on your computer.