ZDoom

Recently, my computer's hard drive failed, so I got another one and reinstalled windows on it. I downloaded GZdoom, opened it up and there's lag, even in software mode, which is strange, considering how this is the same computer where GZdoom was running just fine. I downloaded the latest drivers for the amd radeon 3100 card using the catalyst control center, still lagged. I assume it's something to do with the settings that I have for GZDoom, but I cannot find for the life of me what setting is making it lag.

The only other thing I can think of is that I need to download more drivers, but I still don't know what to do exactly. Any help?

Is it a different version of GZDoom than before? Do you have all the Windows updates up to the point you had them before? Same Windows version? Or maybe the issue is new with AMD's latest drivers which wouldn't surprise me since every version for my R9 270X seems to have a different problem.

It's a different Windows installation and that may make all the difference, especially when it comes to hardware that has been put on legacy support - both by the manufacturer and by GZDoom itself.

What Windows version are you using? Considering that the card is more or less obsolete I'd expect it to cause issues if some more recent version was used.