running two copies of prime95 in the same machine

[rx7350]

Get a 'command prompt' (or DOS prompt) window started - change directories to the PRIME95 folder - issue the the command 'PRIME95 -A1'. Set the affinity for the first instance to '0', and the affinity for the second instance to '1'

There may be other ways to do it, but this is how I do it.

If you just happened to have a quad-core, the commands would be 'PRIME95 -A1, 'PRIME95 -A2', and 'PRIME95 -A3' to get the 2nd, 3rd, and 4th instances going

Make sure you change the ID on each instance to a uniquely identifiable pc ID to differentiate each instance from the others

From a desktop:
make another link to prime95 or a copy of existing one.
open "properties" (with right mouse button, e.g.)
change "C:\Program Files\Prime95\Prime95.exe"
to "C:\Program Files\Prime95\Prime95.exe -A1"

Second copy of Prime95 creates in the same directory files prim0001.ini etc

[ewmayer]

All your copies of prime95 is belong to us.

[WsF]

Make another copy of a link (shortcut) to Prime95 at your desktop. You can do it copying the previous one and it wiil be named "Copy of (whatever)" or by dragging from Prime95 directory/folder. Nevertheless.
Open Properties (with right click, e.g.) and change
"C:\Program Files\Prime95\Prime95.exe"
to
"C:\Program Files\Prime95\Prime95.exe" -a1

Of course names of folders can be different in your case but it is a standard.