The Dell Dimension 8400 Failure Code 7

by Ruri Ranbe

The message "Return Code: 7" appears when the Dell Dimension 8400 detects a problem with the hard disk drive. This error occurs when the computer is unable to read the data contained on the drive.Seeing this message means that the drive is failing -- or is about to -- but sometimes the disk can be salvaged for a short period of time.


90/90 HDD Diagnostics, built into the basic input/output system on the motherboard, is one of the most reliable hard drive tests available through Dell. The name refers to the accuracy of the test -- 90 percent -- and the amount of time it takes for the test to determine the health of a drive -- 90 seconds. Pressing "Ctrl+Alt+D" on the Dell screen will boot the Dimension 8400 into 90-90. Since 90-90 is inaccurate about 10 percent of the time, it's important to run the test twice to confirm that no false positive or false negatives have occurred.

Dell Diagnostics

Dell Diagnostics can be run from the utility partition on the hard drive; pressing "F12" on the boot screen will open the menu to access Dell Diagnostics. Unlike 90/90 HDD Diagnostics, Dell Diagnostics is much more thorough; it can run express, extended and custom tests on all the hardware installed on the Dimension 8400. If a test fails, Dell Diagnostics reports the results and includes support tips to resolve the issue. Running an express, then an extended test on the Dell PC is recommended, since the hard drive error could be caused by another problem with the computer. Note that if the utility partition is corrupted, Dell Diagnostics can be accessed instead from the Drivers and Resources CD.

Bad Sectors

Hard drives are made up of tracks -- concentric circles that wind around one side of a hard disk. Since tracks are too large to hold data, they are separated into sectors that can accomodate 512 to 4,096 bytes of data. Bad sectors are those that have received physical or magnetic damage, thus rendering the data in the sector inaccessible. Since the Dimension 8400 can't read the data found in a bad sector, if the hard drive contains many bad sectors, "Return Code: 7" may appear when running a diagnostic test on the drive.


CheckDisk, or CHKDSK, locates and "repairs" bad sectors found on a hard drive. CHKDSK does not technically fix the bad sectors, but rather marks them off so that the computer won't attempt to read from or write to them in the future. If you have a full edition of the Windows XP CD, you can run CHKDSK from the Recovery Console found on the disc, but if no such CD is available, you must use a third-party tool instead. Note that repairing bad sectors is a temporary solution that can give you just enough time to rescue the data on the drive before it stops functioning altogether.

About the Author

Ruri Ranbe has been working as a writer since 2008. She received an A.A. in English literature from Valencia College and is completing a B.S. in computer science at the University of Central Florida. Ranbe also has more than six years of professional information-technology experience, specializing in computer architecture, operating systems, networking, server administration, virtualization and Web design.