In the case of whitebox computers, we usually diagnose the problem, (which seldom takes more then a few minutes) replace the bad part, and get a replacement from the manufacturer. You can often have your computer back the same day or the next.
In the case of Dell or other name brand manufacturers, they usually want to do a fairly extensive diagnosis over the phone to verify that the problem is hardware and not software (which is not covered by warranty), and that they are confident that they will be replacing the right part. This telephone interview may be as short as 10-15 minutes, but often takes 1-2 hours including the time on hold, or to restart the process if your call is dropped, and the time to get you to the right department. In the case of Dell, you can start at 1-800-WWW-DELL (1-800-999-3355). If you are having problems with a Dell you can go through this process yourself, or you can ask Computing Staff (usually Dan Heindl) to call for you and arrange for repair. We can often expedite the process because we usually know what the problem is, can describe it in technical terms, and know what parts are needed for repair. Once the Dell representative agrees that there is a hardware problem and approves the repair, the repair part is usually brought over and installed in 1-3 working days (The Dell warranty specifies next business day, but sometimes there are problems with shippers, or parts and it takes longer).
If you setup an account on the Dell Website you can get information about your Dell PC such as the date of purchase, the original purchaser and shipping address, how much time is left on your warranty, what components were in your PC when delivered, etc. Computing has such an account, and can lookup this information for you if you ask.
A special, and very common, case is what happens if your hard drive fails. Certainly, any warranty, if in force, will replace the hard drive, but not its contents. The hard drive contains your operating system (Windows XP in most cases), any installed software (such as Microsoft Office or Publisher, Email clients such as Thunderbird or Eudora, web browsers such as Firefox, Mozilla, Netscape, Adobe products such as Acrobat Reader or Writer, Pagemaker, Illustrator, Dreamweaver, and InDesign, miscellaneous software such as SPSS, WisCal, Palm software, printer drivers, CD or DVD software and CODECS,and other software you may have installed). Perhaps more importantly it will have all the documents you've created, and the data you've collected that you have not saved on a network drive (the recommended storage location for documents and data). It will also contain anything else you've placed on your computer such as photos, or downloads, or in many cases bookmarks (or favorites).
The operating system and some installed software will be replaced on the new drive by reimaging (usually about 4 hours not covered by warranty). Other software and drivers will be reinstalled as needed, but you may have to provide the original media that came with the machine(for drivers) or software and show proof of valid licensing (these installations could take anywhere from 15 minutes to several hours, also not covered by warranty). If you no longer have these media, they can usually be ordered or downloaded, but this often adds a significent amount of time (and therefore cost) to the recovery process. If we get the failing drive soon enough, we may be able to recover some or all of your documents and data and transfer them to the new hard drive (this takes at least an hour, and usually several hours, also not covered by warranty).
Hard drives are quite persnickety. They may run with no problems for a decade or more, or they may fail a week after you've gotten your new PC. They may be working fine and then, within a few seconds be totally unreadable, or they may gradually fail over a period of hours, weeks, or even months.
In a few cases, people have suspected that their hard drive had begun to fail, have brought us their computer immediately, and we have been able to save the operating system, installed programs, documents and data without the many hours of labor described above. In most cases, people report that the machine was working fine one day, and when they came in the next morning it wasn't working at all, or it had been acting strangely for hours or even weeks, but they kept using it until it became unusable. In the latter two cases, the operating system and installed programs will not be recoverable, and documents and data are usually not recoverable, or only a few are recoverable and it takes hours to recover them.
The moral here is this. If your computer starts to act strangely, or you suspect a hard drive failure is imminent you should shut the computer off (minutes often do count) and give us a call with a description of what it is doing. We may be able to save many hours of labor, and some or all of your documents and data.
A second moral might be that while warranties have some value, they rarely result in totally free repairs - especially if you count your time in contacting the manufacturer, working through the diagnosis with the technician, and arranging for a technician to come out and install the new part at a time when you are available to let them in the room where the computer is located.