Inspector Jihad, the first reply in the locked thread answered your initial question, and others answered your other question(s). Why are you multiposting the same topic?
Here's my reply from a recent thread:
Keep in mind that (unbranded) OEM operating systems are cheaper because 1) you don't get support from MS and 2) it cannot legally be transferred to a new computer; it is tied to the original sytem that it's installed on. OEM DSP software does not require a piece of hardware to be bundled with it. If you cannot find DSP then then a $2.00 internal power splitter meets MS requirements for OEM operating system purchases. Retail operating systems can be transferred to new computers and you get support from MS. This is why retail costs more, but in the end it's a better value.
Be careful who you purchase software from since a lot of shady companies sell grey market, and other software that should not be resold, for a discounted price.