Dell Inspiron 620 Desktop, Intel Core i5, 3GHz, 8GB Ram, Windows 7
I've had this problem for at least 2 years and it is driving me crazy, I cannot find a solution.
My computer is constantly freezing up - it stays frozen for a minute or two and then comes back.
Happens often when using Youtube, Skype or a site with lots of flash banner ads.
I remember the problem starting back when I was trying to install drivers for a USB 3.0 port that I eventually gave up on. Recently tried re-installing the drivers for my USB ports and that did not fix it.
Ran the Support Assistant and it did not find anything wrong with the CPU.
It's probably an Operating System/driver issue. Likely you need A Clean Install of Windows would help, at this stage I'd recommend clean installing Windows 10 Version 1709 using your Windows 7 OEM Product Key (or by use of a genuine ticket see the special case 3.1):
Windows 10 should have all the drivers required for this Desktop. P.S. are you using a USB 3.0 PCI-e card?
If you have a western digital GREEN hard drive this is the issue.