Theme Hospital Resolution stuck at 640x480

I've installed my old trusty Bullfrog "Theme Hospital", the 2002 version inside a Windows XP virtual machine. The game works well, but is stuck in 640x480 resolution as in the following image:

This results in a huge border around the game and makes the game harder to play. The listing of files is given below (minus directories):

Directory of C:\Program Files\Bullfrog\Hospital
09/08/2002  09:22            35,328 AweMan32.dll
04/06/2016  20:52            26,986 DeIsL1.isu
04/06/2016  20:51                56 Hospital.Cfg
09/08/2002  09:23         1,074,688 Hospital.exe
09/08/2002  09:23                85 Modem.ini
09/08/2002  09:23           144,384 Mss32.dll
04/06/2016  21:18             6,256 NETPLAY.TXT
04/06/2016  21:18             1,395 README.TXT
09/08/2002  09:23            71,168 Smackw32.dll
09/08/2002  09:23           109,056 WSnd7R.dll

The Hospital.cfg file does not have any interesting options. Its entire listing is:

INSTALL_PATH=D:\Hosp\
INSTALL_TYPE=MAX
LANGUAGE=ENG

An the in-game options don't offer any help either. How do I get better resolution? Even 800x600 would make the game easier to play (toug 1024x768 would be ideal).