Windows 7 - No Internet, Win7 boots up into black screen

This is a strange one. Once or twice my Windows 7 has booted up, post, then blue screen with welcome, then it goes into a black screen with a mouse (not hung it can be moved). Answer, log on to Netgear router from another computer and reboot it! Then by magic the desktop in the win 7 computer (wired to network) magically comes alive and a full desktop appears. Have tried rebooting with network cable out - still the black screen. Sometimes on lease renew on router this limited connectivity occurs - but that should not be the issue. Can the desktop hang if no internet connection is present - very weird. Any one else come across this problem. Mike

Try booting into safe mode with the cable out. If it's a program that is autostarting safe mode should disable it temporary.

Also do you know when this started or has it always be like this?

It has not always done it, but is definitely a function of the router's condition which seems strange. Never had to boot into safe mode with 7, dont know how to do it. When it has the black screen with mouse pointer, I can do alt+ctrl+delete to get the blue screen and log off, then it comes up with the log screen, but soon as I hit log on it goes back to the black screen i.e. it cannot load the desktop. While in black mode, reboot router and by magic (without any intervention) the desktop appears. M

press F8 while the computer is booting try safe mode with networking and without. If this is happening after login it sounds like a startup problem to me.

if safe mode works correctly we will have to find what startup programs are causing this

I use ccleaner to ensure no rogue start ups or programs that just love to be added to the startup either directly or via registry, nothing unusual there. I do not have the same problem with laptops running Windows 7.