If you're not going to go above you're current 3GBs of RAM then moving this to a 64bit version of Windows and doing a clean install would be unnecessary. It sounds like you are operating on some pretty old hardware if you only have 3GB of RAM and a Core2Duo, something that probably came late in XP life or in the Vista era. If you're not looking to add an increased work load for yourself then I would just do an in place upgrade to the 32bit version of Windows 10, upgrading to a 64bit system on a machine like that isn't going to help you out.