Este problema es debido a un bug del driver del controlador de teclado y se puede dar tanto en máquinas físicas como en virtuales. Para solucionarlo, basta cambiar una clave del registro como se indica a continuación (extraído de http://keyliner.blogspot.se/2009/11/windows-7-slow-keyboard-response.html).

For desktop computers, there is a PS/2 DIN keyboard bug in Vista and Windows 7 that was originally fixed with a registry change. When Microsoft released Windows automatic update KB977074, the registry change broke and then alternately worked, depending on subsequent Microsoft updates. This is the fix that I am currently running and this resolved my keyboard-speed problem.

Update: Recent Microsoft patches in late April, 2010 or early May, 2010, and again in June, 2010, have done and then undone the changes recommended in this registry hack. I have now switched this solution one way or the other on three separate occasions; each time it fixed the problem. Since June, 2010, it has been solid. Read below for more details.

a. Start, Run, "Regedit"
If the RUN command is not visible, see this link.

b. Tunnel to this key:
Hkey_LocalMachine/System/CurrentControlSet/Services/i8042prt/Parameters

c. On the detail side, "other-mouse-click" a blank area and add a new Dword-32 value. Name the key "PollStatusIterations" (no quotes)

Set value to Hex = 1

Caution, there are other registry keys with similar names.

d. Close Regedit and reboot.

e. If this value is already in the Registry, disable the key by renaming it to "xxPollStatusIterations" (Other-mouse-click, Rename). Reboot and test.

Reason: Depending on which MS patch has been applied, this registry change can re-introduce a slow keyboard problem. You will have to experiment with adding or removing this patch. I've switched this value on or (x) off three times. This is unfortunate. But in each case, it has dramatically fixed scrolling problems.

(Click image for larger view, "Back" to return)

Clearly, Microsoft is having troubles in this area. Expect to return to this value as Microsoft continues to work on this.