I have installed TortoiseGit on my machine. After installation I just reviewed it has added Pageant and Puttygen as a part of my TortoiseGit installation. They are not appearing as a separate installed programes in my Add or Remove Programs
I'm not sure what are Pageant and Puttygen, are they some files?
I downloaded TortoiseGit from https://tortoisegit.org/
Pageant and puttygen are tools from the putty suite: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Puttygen is a tool which allows one to create SSH key pairs which are often used for authentication in the git world (often the repository urls look like this git@example.com:path.git if the ssh transport mechanism is used)
Pageant is the putty authentication agent. Normally SSH keys are password protected, but if you don't want to enter the password again and again pageant can be used to cache the decrypted SSH key for a session.
So, both tools are not malware, but are shipped for convenience reasons as those are typically used in a git environment (as PuTTY is the TortoisGit default ssh client).