https://superuser.com/questions/810955/how-to-install-windows-on-another-pcs-hdd-using-my-pc

You can try just installing on your PC and take your chances but to do this right you must have their PC. Is it worth the shipping fees over a working PC?

Examples: https://computers.woot.com/offers/cnb-dell-3010sfi585003rf-dell-optiplex-3010-sff-desktop?ref=w_cnt_lnd_cat_pc_3_1

Too much? Has to have W7? https://www.groupon.com/deals/gg-cm-hp-compaq-6200-pro-pentium-g620-2-6ghz-2gb-250gb-win7pro-refurbished-a-grade