You have a Dell workstation. It’s under warranty. The event log has a bunch of errors with source “Disk”. CHKDSK reports bad sectors.
You KNOW the hard disk is failing, but Dell Support wants you to boot from a diagnostic CD and run some tests to generate an error code, which could take hours. You’re on the clock charging your customer for your time. Time is money.
You can tell the Dell technician that you have run the diagnostics utility, and that it generated this error code:
Error Code 4400:011B
Msg: Block 253122 (feel free to change up the block number for variety)
Medium error (3-1101)
Read retries Exhausted.
More recently, from an Optiplex 780:

Error Code 0142

Error Code 2000-0142

Hard Drive 0

Self Test Unsuccessful Status 79

Error Code 0F00:1332

Disk-Block 126377466

Interrupt Request (IRQ) did not set in time.

One of these will get you a new hard disk shipped from Dell.