In addition to installing drivers (obviously), here's what else I do for each OS install:
All Windows Versions: Tick "show all hidden files" and untick "hide known file extensions" in folder options, and install Firefox/similar legacy forks (if I intend on going online)
Windows 95: Turn on DMA for all drives, install USB supplements (if the computer has USB), rloew's USB mass storage drivers (if I intend on using my flash drives), and Plus! 95.
Windows 98: Turn on DMA for all drives, install NUSB33E (if I intend on using my flash drives), 3D Pinball (from Plus! 95), DirectX 8.1 (if my video drivers require it), WMP7.1, and IE5.5/6.
Windows ME: Disable System Restore, install DirectX 8.1 (if my video drivers require it), update WMP7.0 to 7.1/9, and IE5.5 to 5.5SP2/6.
Windows 2000: Install Service Pack 4, DirectX 8.1 (if my video drivers require it), WMP7.1/9, and IE6.
Windows XP: Install Service Pack 3 (if the computer's powerful enough), copy over the WMP skins/visualizations from RTM, patch uxtheme.dll, and install some of my favorite themes (including Royale Noir, Watercolor, Embedded, and Longhorn themes).
Windows Vista: Play InkBall and Purble Palace.
Windows 7: Install some updates (if I intend on going online).
Windows 8.1: Disconnect from the internet before installing (to avoid setting up an MS account) and install Classic Shell.
Windows 10 (non-LTSC): Reformat the hard drive and install Linux or 10 LTSC.
Windows 10 LTSC: Disconnect from the internet before installing (to avoid setting up an MS account, disable all telemetry, and install Open Shell.
I still post here, but only occasionally.