TCL wiki has explained the Hard Disk installation of TCL in a very nice way - step-by-step !
wiki.tinycorelinux.com
I have installed on HDD partitions a nimber of times with diff partitions configuration successfully.
But instead of using GParted / PartitionMagic or any third party partiion manager, I used Knoppix Live CD to do the steps which were supposed to be completed in the partition manager as suggested in the wiki.
Also there is no need to lose any data on your exsting HDD - only you should have some free un-assigned free space left on your HDD to create a new partition to install TCL ( minimum 100MB for TCL and another 128MB or more for a swap partition ).
The rest is to be done as explained in the wiki.
Hope this helps !
~ Pats