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#21
You can keep HD plugged in as secondary to boot if needed using one-time BIOS Boot menu key.
When ready to get rid of the OS I'd wipe the HD with Diskpart Clean Command to clean boot code from the boot sector which can sometimes interfere, then repartition as a data storage drive: Partition or Volume - Create New.
What size is the SSD? If large enough I'd put OS, Programs, and data on it. But if it gets crowded copy your User folders to HD, then rightclick each to add to the related Library - Include a Folder - Windows 7 Forums. Once they show up there, delete content of the C User folder but leave it in the Library so you can see if anything gets written there and drag it to the HD User folder.
Only if the SSD is too small would I uninstall lesser used programs to reinstall them to HD, cut paging file to 2 gb, consider disabling Hibernate file which is really quite convenient.