Just a coincidence but I cleaned a friends laptop yesterday which was now taking a good 'FEW' minutes to boot up.
Anyway, long story short version:-
Turned out to be a 'O2 Dongle' he had installed fairly recently and the only thing I can presume was as the PC was starting it was instantly looking for the dongle, but because it was not plugged into the PC then obviously it could not find it until 'EVENTUALLY' it gave up looking for it.
Removed the dongle software, (which he never used anyway) and the PC was back to booting within a minute.
Still on a dongle problem.
I also have a O2 dongle (but never actually used it) but I also remember after trying it, I then had to go back into my network settings and re-change some information that the dongle software had taken over, text change as below.
''When finished using the O2 dongle, make sure to re-enable 'Use Windows to configure my wireless network settings' in:-
Network Connections >
WiFi Connection >
Properties >
Wireless Networks...''
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If anyone is running short of space on their (normally) C: drive, then reduce the setting for 'System Restore' from 12% down to about 6 or 7%, the chances are that going back that far would not be needed and more often than not restore points going back that far will not usually work anyway.
Also disable the restore settings for all other drives/partitions, except for the operating drive/partition because they do not do anything anyway except take up space, System Restore only needs to be set for the operating drive/partition.