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If it was a cmos battery problem then the time and date should be wrong every time you boot up, it would also hang at the bios screen not whilst windows is loading.I would start by looking at the drives as you have already run scandisk to confirm the hard drive is healthy the next step would be to disconnect the cd/dvd drives (link showing connections here) if it boots normally then you've found the problem. If not then I would check through the bios settings to ensure all drives are identified correctly. If everything appeares to be correct but the computer still won't boot normally then I would strip it back to a barebone system & rebuild it one component at a time until I found the problem.