Appears to work in Vista, 7, and 8. A whole lot of web references are out there on this. Just one example:

http://helpdeskgeek.com/windows-vista-tips/manage-irq-settings-windows-vista-7/

One studies a list of IRQs and related hardware, and then choose the hardware to maximize priority upon using registry adds. Use msinfo32 (Hardware Resources, IRQs).

We then add registry entries here:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\PriorityControl

It is reported best to include IRQ zero (0) and eight (8) to start with, this is system timer and real time clock. To do these two, add the following-named items as DWORD in the above area, value 1 for the first, value 2 for the second:

IRQ0Priority
IRQ8Priority

When originally looking at this, I was solving a tendency for my softphone to cut out during any load situation or drive access, and so I checked my PC using Device Manager and msinfo32 as above, and also added subseqeuent priorities:

IRQ7Priority
IRQ20Priority
IRQ21Priority
IRQ4294967288Priority

because on this box, 7, 20, and 21 were USB, and 4294967288 was the active NIC. After you have made the changes, reboot.

The above also produced much better response to VNC and RDP redirection via Labtech.

At least one resource states that one must not set the same priority to multiple IRQs. Duplication may be the source of some reports saying it is placebo effect. Here is a very interesting post with some seriously good-quality testing and results:

https://www.tenforums.com/performance-maintenance/140553-regedit-priority-control-irq.html#6