Actually, this is not as shady as some people around here seem to think. Microsoft has gone on record (if interested, google for articles on PCMag and ARS Technica) stating they don't mind consumers buying "OEM" versions as long as they comply with the terms of the license. The key points here are 1)
you are responsible for end-user support (i.e., yourself, family members, etc.), 2) the software cannot be transferred to another machine, and 3) as a "system builder," you are responsible for installing the software on a fully-assembled computer system prior to distributing it to "end users," i.e. your family. You can read the full system builder license at
http://www.microsoft.com/oem, but I've reproduced the most relevant section below with emphasis added. Note that the definition of "system builder" is very broad--you qualify as a system builder if you are a pre-installer of software on computer systems. You install software, don't you?
1. AUTHORIZED DISTRIBUTION AND ACCEPTANCE. Distribution of individual software licenses or hardware units
contained in this Microsoft® System Builder Pack (package) is not authorized unless you accept this license. You
accept this license when you open this package. By accepting this license, you agree that you are a system builder. If you
do not open this package, you may deliver it to another system builder. System builder means an original equipment
manufacturer, an assembler, refurbisher,
or pre-installer of software on computer systems. Distribution and distribute
means the point in time when a fully assembled computer system leaves the control of system builder. A fully assembled
computer system means a computer system consisting of at least a central processing unit, a motherboard, a hard drive
(internally mounted (Solid State) NAND and/or internally mounted revolving magnetic-based hard drive), a power supply,
and a case. If you are pre-installing Microsoft® Windows® XP Starter Edition or Windows VistaTM Starter, the fully
assembled computer system must also satisfy the hardware requirements listed at
http://oem.microsoft.com/starter. If you
choose not to accept this license, promptly return the unopened package to your distributor. Individual software licenses
or hardware units cannot be returned after this package is opened.