Change display resolution and do full screen for apps from Windows 7 XP Mode?

I'd like to run some semi-old children games on my Windows 7 x64 machine, but they were made for the Win16 API which is gone from Windows x64. Thus, I have installed the games in XP Mode, which works fine, except for the screen resolution.

On a native installation the games' 640x480 resolution will go full screen and fill the whole display, but in XP Mode I just get a small area in the middle of the screen.

Can full screen be configured somehow? (I've tinkered with the Compatibility settings in XP but to no avail.)

Or are there other virtualization products that do better in this area?

UPDATE: Here's more info on the results of Compatibility settings:

As an example, I can make one of the games run natively on Windows 7 x64 (the others won't) through some installation hacking. It will run mostly successfully if I set the following Compatibility settings:

• Compatibility mode: Windows 98
• Run in 256 colors
• Run in 640x480 screen resolution
• Disable desktop composition

and will switch the display mode to 640x480 and fill the whole screen.

Now, if I set up the corresponding settings inside XP Mode and run it from inside the XP Mode desktop, the game will first complain about running with >256 colors (so it seems the compat settings have had no effect) and will then display in the middle with the rest of the XP Mode window filled with black.

If I run the game as a virtual app from the Windows 7 start menu I get the game positioned in the middle of the screen, but the game window is all black while still playing audio and responding to game keys.

Or are there other virtualization products that do better in this area?

I would suggest Oracle VirtualBox if anything. If you have the money though, purchase a license for VMWare Workstation 7. They have by-far the most support for guest OS integration (Unity).