Dumb question, I'm sure!

What is the best way to reduce texture sizes? If I change the scale to .5 in X and Y, does this have the same effect as bringing the texture in to a photopaint program and reducing it, at least memory wise?

The reason I ask is I have a system with 2 GB RAM, and i have a scene with 239,000 polygons that is crashing Vue5Inf. Admittedly, the textures are all hi-res. There are 138 seperate textures. I would like to just be able to use the scale function on all textures when I can if that helps. I will say I did try it, and the scene didn't crash on me; but it didn't always crash so I don't know if I fixed it or not.

Thanks in advance!

John