Shouldn't buy a used iPod, you'll have a hard time getting support / repair / a warranty for it.

When you purchase the iPod, it includes;
- a 90 day eligibility for a single incidence of technical support by phone
- a 180 day service agreement that covers any shipping charges for repair
- a 365 day hardware warranty that covers defects and hardware failure

Technical support = $49.00 an issue
Shipping charge = $29.95 per repair
Battery replacement = $99 per battery after warranty expires

However, you can purchase:
AppleCare Protection Plan; $59 ( except in Florida, not available. )
AppleCare Protection Plan for Students; $47; ( not in Florida )

Unlimited Tech Support for 2 years
Service Agreement for 2 years
Battery replacement program for 2 years

So if you buy a used iPod, or have already purchased a used iPod; Might wanna consider the APP.

You can purchase that at any time within the product's original one year warranty.

All iPods are sold within 90 days of the date of manufacture.

Apple serial breakdown =

JQ450BXCPQ7 = 40GB iPod Clickwheel, mfg week 450.

JQ = MFG Plant
450 = Julian date of MFG
BXC = Production run & unit code
PQ7 = Configuration

iPods with a ten digit serial number are HP iPods, and are not supported by Apple - call HP for that.

If you buy a new iPod from a store, their extended warranty does NOT entitle you to the same benefits as the AppleCare plan.

800-SOSAPPL = tech support
depot.info.apple.com = repairs