Very Slow boot after updates

I have a Pavillion DM3 that I have updated to Windows 8 Pro. I have left the Win7 Home on as well and have a dual boot that I was going to keep until I was happy with Win8.

Win8 installed OK on a new partition and ran very well. I loaded some other software like Office and Acrobat, and it still started and ran very well. I then let it apply the Windows and Office updates (about 70 items). It then took about 10mins to boot. Thinking I had corrupted something, I tried the auto repair, but that didn't work, so I tried refresh and rebuilt the Win 8.

I reinstall all the items I had installed previously, and applied the updates again, but exactly the same problem - very slow to boot. I have now reverted to Win7 again, and it is all working fine again. I have left the HP System partition unchanged, and as the active drive. I did try various boot rebuilds but that didn't help either.

There must be something in the updates that causes this but I don't know how to find out what.
Any advise to point me in the right direction would be a help. I am not expecting to know which update is the problem, but more a process to find out.
Thanks

Go to task manager and disable some applications there that you don't want to run automatically on startup.
And I know this is not highly recommended, but I also disable my Auto update and just do manual update from time to time.