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VMWare Tweaker lays bare dozens of hidden VMWare settings

VMWare is a popular virtualization software for Windows. When you create a virtual machine on VMWare, the application saves all the settings associated with the VM on a plain text configuration file having the extension .VMX. The various settings on this configuration file can be edited through the ‘Edit virtual machine settings’ option on VMMare products like VMWare Player and VMWare Workstation.

However, only a part of the settings are accessible through the VMWare GUI. The more interesting features are hidden from the user. Fortunately, as already mentioned, the VMX files are in plain text and thus possible to hand edit them in a text editor. But to edit this file you have to first understand the various cryptic parameters on it. If you don’t want to bother yourself, checkout the open source freeware utility VMWare Tweaker.

Simply load the VMX file into this little tool and instantly get access to dozens of settings you never knew existed. There are some particularly interesting ones to check out. For instance, look under the Time and Clock tabs.


The constant boot clock option allows you boot the guest OS from the same point in time. So whenever you power on your virtual machine the date/time will be always set to the one you specified here.

After you have installed VMware Tools on your virtual OS, the internal VM clock is always in sync with your real hardware one.  The synchronization is performed during different events (while tools startup, snapshot restore, etc.).  Sometimes there is a need to avoid such synchronization (eg. when testing trial software).  Selecting all the checkboxes under Time Sync Options enable you to turn off the synchronization between tools and hardware clock.

The options under Sound and Video tab allows you to customize the video memory size and change the virtual machine’s sound device


Under the Network tab you can change the VM’s MAC address.


The BIOS tweaks are especially useful. You can edit the BIOS of the VM just the way you edit the BIOS of your real machine. Here you can change the default OS, set the boot delay, and enable Physical Address Extension (PAE) to enable x86 processors access more than 4GB of physical memory, in case you have plenty to spare.


Be sure to backup the VMX file before you start editing it.


  1. great post keep up the good work

    instantfundas allways has great postings
    big fan


  2. Most of these settings are readily available within VMware itself. I suppose someone may have an esoteric use for the program; however, it sounds rather silly to make a back up to play with a couple of settings which will do little to increase the performance of the Virtual Machine. Better to tweak the settings of the OS being run--lots of those are missed.

  3. @Jasray, these settings are not available from within VMWare. For example, where do you find the BIOS settings, or the time sync settings?

    These tweaks do not increase performance of the VM but that doesn't undermine their usefulness. Do BIOS tweaks increase performance of your computer? No. But can you live without access to the BIOS?

    And backup is recommended just to be on the safe side.

  4. Drun speaking....

    As for backups - tool is backing up your orriginal VMX by default... just check the VM folder

    New ideas/comments well appreciated


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