Oracle VirtualBox stuck installation

When re-installing Virtualbox, it hangs and nothing happens.

Googling I found the solution:
http://www.tomshardware.com/forum/38226-63-problems-oracle-virtualbox

Pasting the answers here:

VirtualBox doesn't install startup items or services on Windows host, rather it installs several device drivers which may be the ones giving you problems. Depending on your settings during the installation, these drivers should be in your system:  

VBoxDrv VirtualBox Support Driver Oracle Corporation c:\windows\system32\drivers\vboxdrv.sys  

VBoxNetAdp VirtualBox Host-Only Network Adapter Driver Oracle Corporation 

c:\windows\system32\drivers\vboxnetadp.sys VBoxNetFlt VirtualBox 

Bridged Networking Driver Oracle Corporation 

c:\windows\system32\drivers\vboxnetflt.sys  

VBoxUSBMon VirtualBox USB Monitor Driver Oracle Corporation c:\windows\system32\drivers\vboxusbmon.sys 

TAP-Win32 Adapter V9 - VirtualBox Bridged Networking Driver Miniport  

Try using a program like Autoruns to disable those drivers and check the Device Manager for any VirtualBox related entries that may be marked as a problem. If the failed installation still shows on in your Programs and Features, try using CCleaner to remove that entry from the list. Before trying to reinstall again, download the latest release of VirtualBox and make sure the installer's checksum is correct. 
Post a reply if this helps you or not. 

--------

Thanks for those pointers - I think I have now solved the problem!  

Starting with a system that has VirtualBox installed and was thus hanging on reboot I did several 'shutdown->restart's to prove the frequency. I got 4 hangs out of 8 reboots.  

Then I looked for the drivers. I could only find 3 - VboxNetAdp, VboxUsbMon and VboxDrv. (The last 2 are 'hidden - non PnP drivers' you have to enable hidded drivers to see them. I disabled all three and repeated the restart tests: 8/8 success!  

Now I changed the status of VboxDrv and VboxUsbMon from 'system' to 'demand'. That failed first time so I tried 'automatic'. Then I did the restart tests again: 8/8 success. Re enable the VboxNetAdp as well... again success!  

Now I had re-enabled all the drivers so I tried running Virtualbox again with complete success. So far I have had no hangs on restart with those two non PnP drivers set to automatic. (See here for an explanation of driver startup types http://technet.microsoft.com/en-us [...] 25630.aspx )  

BTW the checksum on the package is wrong! Oracle have released a new version of the VirtualBox without updating the MD5 page. You can see the release number of the installer is different from that quoted on the checksum page!  

Thanks again - problem solved!