This can always be some installed product that takes 10 minutes to initialize itself after boot. Security products would be my first guess.
You can test this by booting in Safe Mode. If this fixes the slow-down, then try to turn off one by one (or several at a time) all products that startup with the computer until you find the guilty one. Autoruns for Windows is best for this, as it can undo actions and also can take a backup of the existing startup applications. But better create first a system restore point as an additional protection.
If this does not help, then something is very wrong with your computer and needs repairing. Malware can never be ruled out, but a damaged system is more likely, as Windows Update can also break your system.
I would start repairs by
How to Repair Windows 7 System Files with System File Checker. This requires a Windows 7 installation DVD of the same service-pack level as your installation.
If SFC has found nothing, the next step would be Repair Install. This will only refresh Windows without affecting the installed applications.
If you get your system working again, do Windows Update manually, rather than letting it do so automatically, just in case.
But take backups and ensure you have all the materials necessary to reinstall everything, or that your computer has a recovery partition, since the repair itself might make your computer unbootable.
Best Answer
See this WinTuts' article: Disable User Account Control (UAC) for certain Windows Vista applications. That page is written for Vista, but it probably works on Windows 7 too.