Why are my registry updates ( at boot ) slow?

Question

So, for the past 6 months or so, the Windows 7 registry updates that happen at booting my laptop are going really slow. Where it usually takes a few seconds, it will now take up to 10 minutes.

Any ideas why this is happening?

P.S.: I also tried cleaning the registry with CCleaner.
P.P.S.: It's also not about the number of updates performed, my mother's PC did over 20000 updates within seconds, whereas 6000 updates seem to take forever on my laptop.
P.P.P.S: I defragmented my harddrive, but that didn't help.