XenServer: Manually Set Memory Range.
xe vm-list
Grab the uuid for the VM you wish to modify.
xe vm-param-set -uuid=<uuid> -memory-static-min=1024MiB
xe vm-param-set -uuid=<uuid> -memory-dynamic-min=1024MiB
xe vm-param-set -uuid=<uuid> -memory-static-max=1024MiB
xe vm-param-set -uuid=<uuid> -memory-dynamic-max=1024MiB
You will most commonly use MiB to specify the memory size.
My most common reason for setting this is the Windows 7 template sets the minimum RAM to 2GB, which IS the recommended minimum, but obviously not needed, especially if the VM is doing primarily lightweight testing (testing an install, etc.).