Which bootloader? Grub Legacy with PCLinux or Grub2 with Mint? When you installed PCLinux, did you install its Grub to the master boot record? Or did you install it to its / partition and try to modify the Mint grub.cfg?
Since you are only able to boot PCLinux, I expect you have its Grub Legacy in the mbr. I use PCLinux as a base system with Grub Legacy in the mbr. I am using 2011 so I don't know if they have switched to Grub2, you will have to check. If you have a menu.lst file in PCLinux then you are using Grub Legacy. You can put an entry similar to the one below in the PCLinux menu.lst to boot Mint
You will obviously need to change the partition number on the root line to whatever is approriate. You may need to remove the (#) from before the savedefault and boot lines but I would leave it the way it is and try that first.
If this doesn't work, try googling "bootinfoscript", read the instructions download and run it to get information to post on your drives/partitions and boot files.