It all depends on what type of media it is. As an example, third parties are not allowed to sell OEM Recovery Discs (yet they do) without a computer purchase. They are not allowed to sell OEM/Disty CDs (yet they do) without a hardware purchase. However, Retail media should be just fine. The reason you may see lower prices on Retail media is if they are EOL (end of life) or no longer being stocked by the distributor. You may also see lower prices on SP2/b media as compared to SP3 media. The real problem is that some websites that sell OSes do not use the real picture, but a stock photo. I never buy anything with a stock photo unless I have a history with them. Also, they do not list the part numbers on the media. Some Windows media do not come with COAs and some do! This would be helpful information. Or let's say (for example) you already have a COA but need the media. Well, the part number on the COA needs to match certain part numbers on the media. This is more true for XP and older OSes, Vista and 7 are a little better since you can install those without a product key and just call the Activation Center. Oddly enough, I found one website selling XP media that is listed as "refurbished"...