unreadable HD

hello again.you may be familiar with my problem.i was able to run win xp CHKDSK and recover my stoarage drive last week(actually on numerous reboots chkdsk ran on start/up and recovered)i get the same msg now>drive is inaccessible< although now when i re-boot, chkdsk wants to run on every start/up and says if i want to skip checking drive (i don't),then it gives the msg>>unreadable master file table<< and chkdsk aborts.i know that if i can get chkdsk to run i can recover the drive,its really a smart application but i cant get chkdsk to run.i also tried some of the tips in Q&A,it wont let me fragment or scandisk and i'm also trying to go over everything i did last time sincerely