You did'nt say what version of Windows you are using.But in Windows XP:
Go to Start->Run->Then type chkdsk.Then press OK.
You will see a large black oblong section,with words,telling you what it is doing.You should see the program working.Depending on the size of your hard drive,it could,but probably won't,take several minutes to complete.Just let the program go to work.Let it finish,and it should auto disappear from your monitor.It may,or not,ask you to reboot at the end.
In case you lose data in the future,try this link:
http://www.bitmart.net/r2k.shtml
Read carefully,and try their demo before you buy.