Actually, there is a program you can use to play StarCraft in a window AND stretch the image to a custom resolution.
I have a very basic page set up for the files and instructions:
http://diabloonvista.uw.hu/
here is my review of these programs.
1.) starcraft-in-a-window.rar
pros
-works great.
-as soon as the gameplay starts, mouse is locked in window (good thing)
cons
-have to set desktop resolution to increase window size.
overall i give it 9/10
2.)D3DWindower-English.rar
pros
-has huge array of controls in emulation, all of which run great.
-very fast emulation
cons
-not very user friendly for noobs.
(took me a good minute to figure out that DD was over writing D3D)
-window control mode does not support D3D(8-9)
(look at the control panel, it says only for 1-7)
-D3D has no option controls
overall i give it 6/10