Yes, just like that I'm back to MS. They're necessary to get my work done

Does anyone have a good lead on inexpensive copies of older MS software? I'm looking for Windows older than 8 or even 7, and Office older than 2013. I'm trying to keep the cost down to under $100 for each piece of software.

I'd even go back to XP and Office 2003. Heck, the client I'm helping out is just replacing a computer that had Office 2000 and I think he was happy with that.