Most auto parts places won't tell you this (in a lot of cases it's because they don't actually even know), but it has been the policy of every major AC compressor supplier for a number of years now: unless you replace the receiver/dryer and orifice tube/expansion valve, and have evidence that the proper procedure was followed to install and charge the system, your compressor warranty ends the second you install it. In other words, if you didn't videotape yourself doing it or don't have a receipt with parts and labor charges describing the above, you don't have any warranty. RockAuto explains it pretty well here.
Although I didn't see one listed for my application(s), Four Seasons offers kits that include everything you need to insure the warranty will be honored. The kits are obviously somewhat pricey and even the local shops didn't always want to pay for them, so I would have to note right on the receipt that the compressor did not have any warranty whatsoever since further parts were necessary.
ok, ok, I looked up prices on a drier, and valve, not as bad as I was thinking.