How to Run Windows 7 from a USB Flash Drive

I’m not talking about how to INSTALL Windows from a USB Flash Drive. That’s easy. I’m talking about booting and running Windows 7 in real-time without a hard disk, strictly from a USB Flash Drive.

Microsoft doesn’t want you to do this.  If they did, it would be much easier.  So far, the only way I’ve found to make Windows 7 run from a flash drive is with a virtual machine on Linux.  This was definitely not my first choice due to the performance implications, but it worked, and I’m typing this up on Windows 7 Ultimate running from a Patriot RAGE 16GB flash drive.  Running full-screen, it’s easy to forget I’m secretly penguin-powered.

Here’s the high-level process that worked for me:

1. Make the 16GB+ flash drive bootable to Linux.  Use a 4GB partition, including a 2GB casper file for persistence.  Detailed information can be found at PenDriveLinux.com.

2. Install Oracle’s VirtualBox software on the Linux boot drive.  It’s simple, effective and free.

3. Install VirtualBox on a separate, faster workstation.  Use the faster machine to create a Windows 7 virtual machine.  Use a virtual hard disk that’s 12GB, but starts out smaller and expands as needed.  Note: Technically, you could install and configure Windows 7 directly on the flash drive, but with the slow read/write performance of the flash drive and the unoptimized Windows 7 default install, this will be slow and painful.  I know, because I tried.

4. Optimize the Windows 7 VM.  This step is critical!  Do not skip it. Before you even try to boot it up from the flash drive, install any Windows Updates, and do basic performance tweaks like disabling System Restore and Windows Search.  Also, manually set the page file to 256MB or less. For a virtual RAM setting, 512MB works well.  Too much, and it seems like Windows 7 will spend too much time swapping data around. BlackViper.com is a pretty good source for Windows optimization.

5. On the fast workstation, boot to the flash drive and use GParted to create a 2nd 12GB partition to store the VM.  Windows will not create or recognize a secondary partition on a removable flash drive, but Linux will.

6. Copy the Windows 7 VM from the workstation to the new 12GB flash drive partition.

7. Use VirtualBox to create a new VM using the file you just copied, and you’re set.

In my case, this provided a usable Windows 7 installation that ran effectively from a USB flash drive.  As expected, it’s not a speed demon, but it’s surprisingly usable as a browser or Microsoft OneNote 2010 platform once the OS adapts to your typical usage patterns.  A 32GB Flash Drive or larger would be better — 16GB is a bit cramped.

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