Reading warranties is an art in itself. A few tips:
Beware the deadly modifier "manufacturer's" on a warranty; this means you have to go back to the equipment's original manufacturer in case of problems and can't get satisfaction from the mail-order house. Also, manufacturer's warranties run from the date they ship; by the time the mail-order house assembles and ships your system, it may have run out!
Watch for the equally deadly "We do not guarantee compatibility". This gotcha on a component vendor's ad means you may not be able to return, say, a video card that fails to work with your motherboard.
Another dangerous phrase is "We reserve the right to substitute equivalent items". This means that instead of getting the high-quality name-brand parts advertised in the configuration you just ordered, you may get those no-name parts from Upper Baluchistan — theoretically equivalent according to the spec sheets, but perhaps more likely to die the day after the warranty expires. Substitution can be interpreted as "bait and switch", so most vendors are scared of getting called on this. Very few will hold their position if you press the matter.
Another red flag: "Only warranted in supported environments". This may mean they won't honor a warranty on a non-Windows system at all, or it may mean they'll insist on installing the Unix on disk themselves.
One absolute show-stopper is the phrase "All sales are final". This means you have no options if a part doesn't work. Avoid any company with this policy.
Does the vendor have the part or system presently in stock? Mail order companies tend to run with very lean inventories; if they don't have your item in stock, delivery may take longer. Possibly much longer.
Does the vendor pay for shipping? What's the delivery wait?
If you need to return your system, is there a restocking fee? and will the vendor cover the return freight? Knowing the restocking fee can be particularly important, as they make keep you from getting real satisfaction on a bad major part. Avoid dealing with anyone who quotes more than a 15% restocking fee — and it's a good idea, if possible, to avoid any dealer who charges a restocking fee at all.
Warranties are tricky. There are companies whose warranties are invalidated by opening the case. Some of those companies sell upgradeable systems, but only authorized service centers can do upgrades without invalidating the warranty. Sometimes a system is purchased with the warranty already invalidated. There are vendors who buy minimal systems and upgrade them with cheap RAM and/or disk drives. If the vendor is not an authorized service center, the manufacturer's warranty is invalidated. The only recourse in case of a problem is the vendor's warranty. So beware!
It's a good idea to pay with AmEx or Visa or MasterCard; that way you can stop payment if you get a lemon, and may benefit from a buyer-protection plan using the credit card company's clout (not all cards offer buyer-protection plans, and some that do have restrictions which may be applicable). However, watch for phrases like "Credit card surcharges apply" or "All prices reflect 3% cash discount" which mean you're going to get socked extra if you pay by card.
Note that many credit-card companies have clauses in their standard contracts forbidding such surcharges. You can (and should) report such practices to your credit-card issuer. If you already paid the surcharge, they will usually see to it that it is returned to you. Credit-card companies will often stop dealing with businesses that repeat such behavior.
Gateway: may also be a vendor to avoid. Apparently their newer machines don't have parity bits in their memories; memory is tested only on reboot. This is dubious design even for Windows, and totally unacceptable for Unix.
In early August 2001 I designed an `Ultimate Linux Box' with Gary Sandine and John Pearson of Los Alamos Computers; you can read all about it These guys know what they are doing and are fun to work with. If you need a high-end Linux workstation, or your laboratory needs a computer cluster, talk with them.