Sounds like your OS is on its way out.. I would recommend completing a backup of your data/serial numbers and completing a fresh install of windows.
Most common spec's of this model;
The Dell Inspiron 1750 (2211MBU) features a fairly typical configuration for a laptop in the $700 to $800 price range: a 2.2GHz Intel Core 2 Duo T6600 processor, 4GB of memory, and integrated Intel GMA X4500HD graphics.
It's hardware would eat windows 7 up, It's you Operating System that's damaged.
How to complete a fresh install of Windows 7:http://www.sevenforums.com/tutorials/1649-clean-install-windows-7-a.html