I must assume you are talking about the boot page where it says installing update x of x and 20% done or whatever numbers you have.
I would think you could get into safe mode with the F8 key prior to this time, but I cannot test to find out. Hp may have another way to intercept the boot.
If you can find no way to stop the loop and HP doesn't know, see if you can use the Repair function of the install DVD to restore you system back to where it was before the updates started. Then set Windows to not automatically update.
If that doesn't work, maybe a startup repair from the same area on the install DVD. Let it work up to 3 times to fix your startup problems.
If you do not have an Install DVD and HP did not give you a restore disk of some type, you might be able to download a Win 7 repair disk from the net. I do not know how it will behave with the Win 7 version HP is using.
If you got it at a retail store, could they look at it if HP doesn't help?
What model is it?
I saw some other threads with your same problem, but no solution was shown.