A recurring problem for me over the years is that when I upgrade a mobo, but using the same CPU and the same primary HDD, Windows will no longer boot off that drive. The culprit appears to be the different North Bridge and South Bridge chipsets. Rather than (once again) going through the time-consuming re-installation of the OS and hundreds of applications, I am wondering if there is a simple way to fix the boot sector without destroying any other data. In the current instance I am using XP Pro x64, for which (it is said) there is no Emergency Recovery Console or ERD Commander. Has some Russian genius written an independent "fix boot" utility?
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You need to do a 'repair' windows installation. This will re-install your core windows files and enable you to install your new chipset drivers etc but keep all your installed programs and files. This should be an option from the windows boot CD.
In this case I am using Superior XP Pro 64-bit, a customized and stripped-down edition which does not offer the 'repair' function (I tried it). This is why I am asking for an INDEPENDENTLY-authored solution.