no more undos

Blender is starting to tell me no more undo and I did not use any or should have many left. Im using windows 7, 38 % of 4 gigs that is using 1.52 gigs . I was told windows would only see so much ram. so why buy 8 or 16 or 32 gigs ? Or is there something else going causing this?

Are you using any slider to edit values? If you do that, that will fill up undo fast! Any little changes in value get stowed you know.

Thanks ridix I do not think Im using sliders cause I do not know what they are. I’m modeling in 2.49 and have undo set to 64? I think. Right now Im manually unsubsurfing a model with 6000 faces on this model on this layer. I started seeing the prolbem a few weeks ago on something different.
Thanks
Tony