- Move your VM to a second physical disk to your host OS – maybe even a USB drive if you are on a workstation or Laptop
- Defragment the filesystem inside your VM
- Defrag the pagefile inside your VM – Sysinternals PageDefrag works a treat
- Defrag the drive on your host that holds the VHD
- Defrag the pagefile on your host as well – again pagedefrag from sysinternals
- Install [updated] VM Additions inside your VM – latest version is 13.552
- Configure your anti-virus scanning to exclude VHD files on the host
For the super deluxe list of Virtual Server tweaks you can check his post.