You probably have a bad hard drive.  Download the diagnostics linked below and run diagnostics:

http://support.dell.com/support/downloads/download.aspx?c=us&cs=04&l=en&s=bsd&releaseid=R188840&SystemID=PLX_PNT_P4_745&servicetag=&os=WW1&osl=en&deviceid=3841&devlib=0&typecnt=0&vercnt=7&catid=-1&impid=-1&formatcnt=0&libid=13&typeid=-1&dateid=-1&formatid=-1&source=-1&fileid=258592

How old is the hard drive?  Hanging up on a long format suggests that the drive has bad sectors that the format program is having trouble reading.  If you have a diagnostics disk you should run a check on the hard drive.

The drive returns this code when it has trouble reading sectors.  That along with the problems you had with a long format suggest strongly that the drive has sectors that are unreadable.  The Dell diagnostics should have a section to configure tests for various parts of the machine.  Explore the menu and locate the tests for the hard drive.  You should find a test that works on the platters, reading each and every one.  Try running that.

return code 7 from my sata drive. i read somewhere that a code 7 might not mean anything and should be run again after formatting. but i can't format. is my drive bad or not? how can i tell?