My desktop we bought an extended warranty for...it did come in use, because the motherboard blew out for no apparent reason...
However, the warranty was unfortunately with Geek Squad, who, in their stupidity, first wanted me to pay $90 for "hard drive recovery" (I'm pretty sure the HDD was fine, but those morons swapped it out anyways, and I lost all my data). Second, they insisted that they take my PC and send it off to some other place for repair (it's a Socket A, at that time, I'm sure they had other Socket A boards in their store). When it came back, my PC (an HP) booted with a nice "COMPAQ" screen and then asked me to insert Windows XP Pro CD's (which I didn't have, my system was supposed to have Home Edition)...so what? Another trip to Best Buy, another week without a PC while they fixed the SOFTWARE! Got the PC back, took it home, and thank goodness! Windows XP Home and an HP BIOS...yet IT WOULDN'T CONNECT TO MY NETWORK!!!! Another trip back, they determined my integrated Ethernet card on the replacement mobo was dead, and asked if I wanted a PCI one (no way! a microATX board suffers from too few PCI slots as it is!). So, after yet another trip to the repair center (apparently run by brainless idiots who can't tell a COMPAQ board from an HP board, can't test a hard drive before blankly swapping it, and numerous other idiotic no brained mistakes), it came back...with a working motherboard/Ethernet port and Windows XP...HOWEVER, it only had a 1.6GHz CPU, when it originally had a 2.0GHz (AthlonXP 2400+). Luckily, the one and only intelligent member of the Geek Squad was working that day, and he had the brains enough to change the motherboard jumpers and clock up the CPU to normal (turns out they actually did good, put in an AthlonXP 2600+ 2.13GHz instead of the 2400+ 2.0GHz that was in it before).
I guess as a way of saying "we're sorry", my PC came back with an extra stick of RAM, but I don't think a lousy 256MB is adequate repayment for a month without my PC.
So...lesson learned. If you want a warranty on your PC...DON'T GO TO BEST BUY!!!!!!!!!! and get a MANUFACTURER warranty, not a store one, as the manufacturers built the PC, so *hopefully* they're warranty service will have at least half a brain.
Now that I know how to do all that stuff on my own though (I was just beginning high school [4 years ago] when this happened), I'd just build it myself...no brainless repair people to take your data for no reason, no waiting for people who can't distinguish COMPAQ from HP, no people that install the wrong OS, put in broken motherboards, underclocked CPU's, etc...
I also bought my ThinkPad used for $160 on eBay like 2 years ago...works fine even now (it's probably 8 or 9 years old). I think if you buy a quality product (which HP apparently isn't), then you'll be OK.