USB External Drives
If you bought yourself a nifty USB external hard drive to hold your VM files, you may find it sometimes acts a little sluggish, even occasionally crashing the VM host app (VMware, Virtual Box, whatever). One thing you might want to try is setting the performance mode of the USB device. To do this on Windows 7, right-click on the drive assignment in Windows Explorer, and select 'Properties". Then click the Hardware tab, and select the specific device in the disk drives list. Then click the "Properties" button at the bottom. Then click the "Change Settings" button, select the "Policies" tab and set the Removal policy to "Better performance" instead of "Quick removal"
Active Directory Synchronization
If your VM guests are joined to an AD domain and you find that the guests drop off the domain every few weeks, it's most likely due to the computer account password synchronization getting wacked. This can happen if the machines are powered off longer than the default resync cycle period, or if you reset (roll-back) to a snapshot from prior to the last resync. You can modify this as follows: