blender problem

I currently have about 3 differnent blender projects i am working on and one of them seems to always run slow I dont know why this is can anyone tell me? my computer is fine and the other two projects load up in an instant, for instance whenever I press ctrl z to undo something the hour glass apperears and it takes a few seconds where as the other two projects i am working on ctrl z works in an instant can someone please help me out thanks!

file size might the culprit ?

need more info to be more precise

Salutations

That is probably an indicator that your scene is very large. Look at the top header next to the colored bar, and it shows you the number of vertices, faces, objects, lamps, and the memory usage. Your “slow” scene probably has high numbers.

To alleviate it if the problem is scene complexity, make sure that all the objects’ subsurf display levels are set very low. Separate like objects into different layers with M, and only look at a couple layers at a time. Turning the draw type to wireframe (Z) also helps.

Just a suggestion: try appending the scene from the slow blend file into a clean project, and seeing if the new blend file is any quicker.