Remove hard drive and store it as evidence. Obtain new HDD. Install your OS of choice. Restore data from off-site backups.
Moderate risk - mount the both the old HDD and the new HDD (with Windows already installed) under Linux. Copy the data in Linux environment from old drive to new drive. You can use http://puppylinux.org to access Windows drives from Linux. It has a nice graphical file manager for that, so you will find it easy to do. Once done, remove the drive and store as evidence.
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Remove hard drive and store it as evidence. Obtain new HDD. Install your OS of choice. Restore data from off-site backups.
Moderate risk - mount the both the old HDD and the new HDD (with Windows already installed) under Linux. Copy the data in Linux environment from old drive to new drive. You can use http://puppylinux.org to access Windows drives from Linux. It has a nice graphical file manager for that, so you will find it easy to do. Once done, remove the drive and store as evidence.