Check Disk Utility

Try defrag first

 

          OR

 

A file may be in use,try safe mode

Try this

 

Start/Run and type in
cmd
OK

 

The command prompt window will open

At the prompt type
chkdsk /r   (there is a space before /)
Enter

 

You will have to reboot for it to run

 

If it still won`t work, run the Dell Diagnostics on the hard drive

http://docs.us.dell.com/support/edocs/software/DIAGS/EN/running.htm#starting_the_dell_diagnostics

 

To access them press F12 when you see the dell logo screen, then there will be an option that says IDE or Hard Drive Diagnostics. That will run a quick test, if you want a more thorough test select the option that says Boot to Utility Partition, then select custom test, select hard drive and then run test.