Need Windows 7 SP1 download for custom re-installation of OS

My Windows Updater  has not worked for over a year and there are other OS problems increasingly plaguing my otherwise still-fine-for-me Inspiron 1545 laptop. Microsoft's Help Desk couldn't help me and escalated my problem to an System Engineer who, after trying everything they were able to do, informed me that I need Windows 7 SP1 64-bit OS re-installation media. I cannot use the WIn7 (non-SP1) disc my computer originally shipped with; if I do so, I will lose all my programs and data. 

Please provide a link so that I can download Windows 7 SP1 64-bit OS re-installation media so that I can re-open my Microsoft case file and do a Microsoft-guided custom install to fix my crippled laptop's OS.