Spreadsheet Corruption

[Import King]

I have an issue with Excel 2007. I have been told that my spreadsheets are growing exponentially, and I had no idea it was happening. Apparently when I cut and paste, delete and use other basic functions, this data is still being stored in the background of the spreadsheet causing it to grow at alarming rates. This is causing the spreadsheet to "freeze" and in worst case scenarios, causing the computer to lock up.
Does anyone have any ideas why this is happening, and how to prevent it from happening?
Thanks,

[TechRetard]

just off the top of my head w/o seeing your sheet --- If you have very large spreadsheets with formulas, every time excel autosaves it will take freeze for some time, depending on the size. Also, if you have thousands of rows with multple columns with formulas, anything that triggers a calculation will force all calculations on the sheet to run. If you don't need the formulas anymore, try copy and pasting values so it gets rid of the formulas and just keeps the values.