That you must check with HP for what drivers in what order must be installed. On some PCs you won't see Windows 7 drivers (I didn't check your model) so you may get stuck with the factory OS.
Installed windows 7 on and hp dc7800p, and now the computer will not load after a restart....works just fine with the shutdown mode..restarts with no problem....was running xp and never had this issue...Imagine it is the smps or something......any thoughts?...thanks..

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