Putty download proper source?

Hi,

I installed the putty download from https://winscp.net/eng/downloads.php#putty_additional
but since the installation the Windows machine is running considerably slower.

Is the above link the correct source for putty or could it be malware?

Which package did you install specifically? Your link points to standalone/portable binaries, which do not install at all.

In any case, our PuTTY binaries are exact copies of the official binaries:
https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html