An obstructed fan and an HDD are the only two things that can cause a clicking noise in a PC. Check if there are wires obstructing your case fans, and your CPU fan. If you have a hard disk drive, check if the noise is coming from there, if so, I suggest you move everything in that drive to another drive asap, if you can still access it.
How can you tell that it is slower than the old laptop? Can you give an example or a scenario that makes you think its slower?