Technical questions like that are best left to the experts at Technical Support as they can troubleshoot it directly. It's free by phone or online chat and linked under Useful Links at the top of this page.
That said, I haven't seen that behaviour here in Win 7, Vista or Win 8.1. Just check that everything is up to date, especially IE as McAfee uses IE for display and function, even if your defualt browser is something else.
For 7 it should be IE11. Settings best at default and make sure the add-ons are also up to date.
Can you please provide more information on the issue that you are facing?
I started a full scan. Before starting the scan the total handle count was ~38300. When Scan was running total handle count increased to ~39200. I did not see a huge handle count number.
I have not yet gotten back to experimenting with this. Good to know that the System Process does not get the large handle count for other folk's context. It gives hope that I can isolate something that makes a difference for if the issue happens or not --once I get back to investigating this.
It was interesting that it was the System Process and not a McAfee process that got the large handle count (that turned out to be thread handles). The actual/active thread count was reported as vastly smaller than the handle count.
I will post here again when I have more information. But it may be a while before I can spend the time.
I have isolated the context in which the handle count in the System Process continually increases:
BOOTCAMP partition (NTFS file system) booted with the Macintosh HD partition mounted as HFS and Macintosh HD is actively being scanned.
BOOTCAMP has a Windows 7 Professional x64 context for its NTFS file system.
The scan of the BOOTCAMP partition/NTFS file system itself does not result in the problem. But once a scan progresses to the HFS partition/file-system the handle count increases as described.
(I was apparently wrong before about the increase happening during the NTFS scan as well.)
Running that NTFS partition under Parallels and scanning the Macintosh HD HFS file system does not have the problem. But Parallels does not make that file system visible directly as HFS to Windows.
So overall the problematical handle count increase seems to involve Apple's implementation of HFS for Windows.