The only thing that wear the drive out is using it. The longer you use it the "quicker" it wears out.
Having said that a PC that is mainly doing low disk intensive tasks will last longer than one running lots of high disk intensive tasks.
Don't worry about OS reinstalls and installing / uninstalling programs.
What make and model was it?
The only way i know to prolong a HDD is to use a HDD cooler to keep it cool. Apart from that don't switch the PC on!