OH theres your issues!! Current antivirus (they design to run on current fast hardware) and again, your old hardware. Yeah,,, thats all got to "go" !...I have 25 ish PC/NAS/servers etc running 24/7 here. In my opinion, the solid state drive is the biggest advance in the last decade. My laptop..took 4.5 minutes from off - to complete boot. With solid state drive....38 seconds.
No polite way to put it, as cliche as it is...you are in horse n buggy, delivering phone books to rotary dial phone users LOL!
Antivirus...HA!, my PC at work, oddly, is bleeding edge tech...but, is at a crawls speed, due to .....antivirus etc. That stuff is a a HOG. Keep in mind I have 25 devices going all the time. Since 1995 I've always had 3+ PC running non stop.
Now...ask me what I use for antivirus.....I don't, never used it...never will. I know you next question...the answer is...ZERO....I've never had a virus.....