Performance terrible after installing new gfx card

[Saint.Million]

So I just installed a new gfx card (1660Ti>5060) and Steam is taking forever to log in, and when (if) it does games are running so slow they are unplayable.

I've installed the latest nvidia driver, and I've also ran my system specs through multiple PSU calculators to check that's not the issue.

Any idea's?
Only thing I can think at this point is maybe re-install windows?

 

[Saint.Million]

Seems to have mostly sorted itself out after a couple of restarts.

Will still do the above tips though. Thank you very much for your help.