Mayhemm,
I was doing some thinking, which can be dangerous on my part and I thought of a few other things to try or check.
First, go into the system and make sure the hard drive is plugged into the SATA 0 port. Since you had someone working on the system, he or she may have plugged the SATA drive into another port besides 0. If so, this maybe causing the system to have a delay in finding the drive on another port so the Intel Boot Agent is then kicking in. Click here <ADMIN NOTE: Broken link has been removed from this post by Dell> for a diagram of your system's motherboard from the on-line Service Manual. The diagram notes the location of Port 0. The motherboard should also be labeled accordingly in small print.
Secondly, try changing the mode of the USB Device Setting option in the BIOS. That option can be found under the Integrated Peripherals menu. Try another setting besides High Speed. My reasoning is that system maybe hanging on a USB device during boot up thus causing the Intel Boot Agent to kick in.
Thirdly, try clearing the CMOS. It's possible there was a option set in the BIOS prior to the motherboard being placed in your system that your system doesn't like. Click here <ADMIN NOTE: Broken link has been removed from this post by Dell> for instructions on how to clear the CMOS. Chances are if you call tech support they will have to do it anyways.
Keep in mind that clearing the CMOS will default all your BIOS options back to their factory recommended settings. Not really a big deal since you're probably using most of the factory settings anyways. The defaulting will require you to re-enter the time/date, re-adjust your boot order if you have made any changes, re-adjust your power management options if you have changed them, etc. In otherwords settings that were changed to your personal liking will have to be re-set. If your system doesn't have a floppy drive the defaulting will turn on the floppy drive controller. If this happens and you get a Diskette Drive error on boot up then simply go into the BIOS and turn off the option for the Diskette Drive. The error message will be gone on the next reboot.
Lastly, if there is such a word, I would try a BIOS update. Although there isn't anything listed in the file description related to a fix for your problem, it is not uncommon for a BIOS update to have undocumented fixes and improvements. If anything the BIOS update will help rule out an out of date BIOS as being the cause. Prior to doing the update you should closed out all unneeded Window applications and unplug all unneeded USB devices. This will lessen the chance of the update hanging during the reboot phase of the upgrade.
