The Autohotkey script I just tested and it works (in this case to keep the timer at 2ms).
I had it run on the host (Win2008), and VMs play fine.
SetBatchLines -1 ; Ensures maximum effectiveness of this method.
SleepDuration = 1000
TimePeriod = 3
DllCall("Winmm\timeBeginPeriod", uint, TimePeriod)
DllCall("Sleep", UInt, SleepDuration)
;DllCall("Winmm\timeEndPeriod", UInt, TimePeriod)
The script process uses only 2MB RAM, and the super negligible 80,000 cycles delta (1 sec) on my 2.8G cpu.
It can be compiled to an exe.
For me, it works when running on the host, but it can be set up to run in the guest (only), so the timer is boosted only when an XP VM is run.