While using Windows Explorer, Internet Explorer or anything that accesses the disk drive on a regular basis, the Windows UI seems to freeze. If Process Explorer is open, you'll notice that Hardware Interrupts are pegged. You can still move your mouse cursor, and at the end of the 10-15 seconds any UI actions that you had started will happen, seemingly all at once.
Motherboard with an Intel chipset with integrated RAID support and SATA drives, like most recent Dell Dimension motherboards, but you are not using RAID.
RAID is enabled on the motherboard. As a result, the RAID version of the chipset driver is loaded.
(NOTE: This solution involves changing settings in your BIOS. Modifying these settings if you do not know what you are doing could result in your system not being able to boot up. Please do a full backup of your machine prior to attempting this fix.)
Reboot your machine.
Go into the BIOS settings and look for the RAID settings.
Disable them. (On a Dell Dimension, change the motherboard settings from "RAID Autodetect/ACHI" to "SATA/PATA".)
Save the modified BIOS settings.
Boot into Vista.
Go into any profile; new drivers will start installing that require another reboot.
Reboot when prompted.