If you just want to do Hyper-v you do not need to install Windows 2008.
Use the stand-alone Hyper-v (it is free).
http://www.microsoft.com/hyper-v-server/en/us/how-to-get.aspx
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No issues other than some software will recognize it as a server OS and not install unless you buy the enterprise version... i.e, no free AVG and such.
Most win 7 drivers work fine although some may again have issues with it being a server OS.