The computer is a key piece of evidence in the courtroom, without it they cannot put the OP on the stand claim to ownership of the computer, and point to the person they loaned in to.
How many people would be able to look at a factory HD and say, yep that is mine?
They don't need to have the OP identify it to validate the chain of custody. They could just do something along the lines of the following*:
* Note: Some details of the litany below may be incorrect, as my recall of the rules of evidence for this are a bit fuzzy and the rules probably differ from state to state anyway. But the basic idea is still the same.
Prosecutor: The state now calls Dr. John Doe.
[Expert is sworn]
Prosecutor: Can you please state your name and occupation?
Expert: John Doe, Computer Forensics Analyst for the state.
[Bla bla bla, expert explains his qualifications]
[Prosecutor pulls out hard drive]
Prosecutor: Dr. Doe, I am placing a piece of computer equipment in front of you. Do you recognize this equipment?
Expert: Yes, it is the hard drive from Mr. Cutts' laptop.
Prosecutor: How do you recognize it as such?
Expert: The serial number is 9-9-0-6-9-4-7-X-B-7-1. [for Blade Runner fans: Not fish! Snake scale!] In addition, it contains the marking, JD, which I made on the exterior of the hard drive after obtaining Mr. Cutts' laptop from Officer Schmo and removing the hard drive. [Note: this probably requires that Officer Schmo testified earlier about getting the laptop from Cutts, checking it into the evidence locker, and then removing it to give to the expert]
Prosecutor: What if anything did you do to analyze this hard drive?
[and so on...]