Enable UDMA in Windows XP

Today, I was given the task to completely revamp an old system that is totally clogged with garbage files to give a new life to it. I did a full system recovery by re-installing Microsoft Windows XP to the old Compaq Presario system hoping that may speed up the system. Well, it did but I realised that that there are other areas which can be further tweaked. For instance, I found out that my hard disk drive supports Ultra Direct Memory Access (DMA) up to Mode 5; that is, UltraDMA-100, as some would call it.

Being able to utilise UDMA support, I was delighted, but Windows XP does not set UDMA support for hard disk drive by default. So, in order to do so, I had to edit the system registry. The following illustrates the steps to activate UDMA support.

(learn how to activate UDMA in XP...)

1. Click on Start button, then Run.
2. Type "regedit" (without the quotes) and press OK.
3. Scroll to the following section:
   

   HKEY_LOCAL_MACHINE > SYSTEM > CURRENTCONTROLSET > CONTROL > CLASS > {4D36E96A-E325-11CE-BFC1-08002BE10318}

4. There may be several directories within the section. Locate the DWORD "EnableUDMA66" or "EnableUDMA100". If they are not found, you may have to create it.
5. To create the DWORD, simply click on Edit on the menu, and then New, DWORD. Enter the string:
   

   EnableUDMA66

   or

   EnableUDMA100

   and then click OK to save.

After the reboot, your hard disk drive will be using UDMA support, and you will experience faster read and write operations while running Microsoft Windows XP.