Two more questions . If I buy the retail version of windows, can I change the motherboard without having to reinstall? Also if Microsoft gives you a new activation code, will all the programs stay?
Clean install is recommended purely as it gives rise to less conflicts and hassles caused by old drivers. Once installed, Windows needs to be activated, hence the need for a new key. Activation does not affect installed programs. Activation has to be completed within 30 days of installation.