Nokiamies

Audacity 2.4.2 no longer got official win7 support (source https://wiki.audacityteam.org/wiki/Windows_7_OS) but it still starts and works fine using portable or installer versions

I use Comodo Internet security 12.0.0.6818 which is last to Windows XP/Vista even site claims latest one works. Comodo is not to everyone. It definitions are not top of range. You need enable hips and others and tweak to make it work well. For network security you can do it on network level. Sometimes even router own firewall is good enough as long as you disable vurneable features like UPNP and other automatic port share features

1. No 2. No 3. Reason is that windows 10 is service and need mandotary forced updates. Up to windows 8.1 I was able delay updates until had time to patch and possibly troubleshoot broken stuff. Second is win10 keep changing too much. My Asus P4P800 mainboard worked all way trough every windows xp service packs using same old drivers while win10 stopped working on my intel atom based system on one update. And I am slowly moving to linux

Do you have Speedstep, CStates and C1E enabled in bios and do you have latest bios? Those three options controls idle and lower cpu states on Intel processors

I desired use different approach and used Windows media player 9 series + ffdshow beta6 rev2527 and Combined Community Codec Pack (dated 2010-10-10) on my windows 2000 laptop that have Pentium M and intel gma 900. With those I can play all of my downloaded/existing video files pretty even 720p ones no lag at all. Those codecs works media players 7-9 under windows 2000 vanilla on my tests.

If you need latest offical win2000 nvidia driver you can use this https://www.helpjet.net/dl/47677297-83974762-53425856/76952134/NVIDIA_169.06_Win2KXP.zip that had support up to 8xxx series under win2k.

What power profile you use? Balanced, power saving or high performance? If high performance try set minium cpu state to 1-5% instead of 100%. That caused R7 2700X run hot and full clock speed on me with windows 7

Only way I have found to download updates to vista now is to use Wsusoffline. Few weeks ago, xp, windows 2000 and windows vista updates stopped working atleast on my end. I got backup of localised updates to win2000 and XP but not to vista.