is there a reason why the installer asks you to scan for malware

i just reinstalled comodo firewall pro and it asked me to do a malware scan but i did not. should i have and would there be a difference if it found anything?

Yes, there is a reason for it. By default I believe Defense+ is installed in “Clean PC Mode” & that mode makes the assumption that everything on your PC is clean (not infected). So, the scan for Malware is a method to double check that logic. In addition, on install if you reject the Malware scan you’re then asked if you’re sure that the PC is clean. Answering yes results in Defense+ being placed in Clean PC Mode, whilst answering no places it in Safe Mode (this mode doesn’t implicitly trust everything on your PC). I hope that helps.

i told it not to scan but if i was wrong about malware could it have infected the install?

Not CFP’s installer, no… or rather I strongly doubt it. It’s more to do with everything else on your PC. However, you can run the Malware scan manually at any time you want. Assuming you have CFP 3 (CIS 3.5 is a bit different), then I believe it’s under the Miscellaneous tab on CFPs main GUI.