after reinstalling windows in drive C can i use the programs that i previously installed in the C drive . Is there any way to run those programs or do i need to reinstall all the programs???

If you performed a "fresh" install (partition/format etc) of XP then you will have to reinstall all/any programs which are not "stand-alone". (Anything which writes entries into the registry.)

If you did a Repair Install then your programs should still be functional.