With titlese/titletocyou can do it. To mimick the formatting shown in your question, I had to load the etoolbox package in order not to include the table of contents in itself. As it seems to be rather complex to patch the abstract environment, I suggest you turn it into a \chapter* command. I supposed you were using the report class, which has no \front/mainmatter commands, so I provided them, to have roman numbering for \frontmatter — actually, I used small caps roman numbering (an old tradition in French typography), but that's easy to change if you don't like it.
\documentclass[11pt, a4paper, twoside]{report}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{heuristica}
\usepackage{microtype}
\usepackage[pagestyles, explicit]{titlesec}%
\usepackage{titletoc}%
\usepackage{etoolbox}
\newbool{addtoc}%initial value: false
\pretocmd{\lsstyle}{\SetTracking[no ligatures = {f}]{encoding = *}{50}}{}{}%
\titleformat{name = \chapter}[display]%
{\lsstyle\bfseries\Large\filcenter\vskip-4\baselineskip}
{\LARGE\chaptername~\thechapter}
{0.5pc}
{\vspace{0.5pc}\Huge#1}%
\titlespacing{\chapter}{0pt}{3\baselineskip}{8\baselineskip}
\titleformat{name=\chapter, numberless}[display]
{\vskip-4\baselineskip\lsstyle\bfseries\itshape\large\filcenter}
{}
{0.5pc}
{\vspace{0.5pc}#1}%
[\ifbool{addtoc}{\addcontentsline{toc}{chapter}{#1}}]%
\titlespacing{name = \chapter, numberless}{0pt}{2\baselineskip}{8\baselineskip}
\titlecontents{chapter}[0em]{\lsstyle\smallskip\bfseries}%\vspace{1cm}%
{\contentslabel[\chaptername~\thecontentslabel]{0em}\hspace{5.6em}}%
{\renewcommand\thecontentslabel{\relax}\itshape}%numberless%
{\hfill\contentspage}[\medskip]%
%
\titlecontents{section}[4.25em]{\smallskip}%
{\contentslabel[\thecontentslabel]{2em}}%numbered
{\hspace*{-1em}}%numberless
{\hfill\contentspage}[\smallskip]%
%
\titlecontents{subsection}[7em]{}%
{\contentslabel[\thecontentslabel]{2.75em}}%numbered
{\hspace*{-1em}}%numberless
{\hfill\contentspage}[\smallskip]
\renewcommand*{\contentsname}{\upshape TABLE OF CONTENTS \vspace{3\baselineskip}\par \hrule height 1pt\vskip1.5ex Contents\hfill Page No \vskip 1.5ex\par\hrule height 1pt\vskip -8\baselineskip}%
\apptocmd{\tableofcontents}{\booltrue{addtoc}}{}{}
\providecommand\frontmatter{\renewcommand\thepage{\scshape\mdseries\roman{page}}}%
\providecommand\mainmatter{\clearpage\pagenumbering{arabic}}
\begin{document}
\frontmatter
\tableofcontents
\chapter*{Candidate’s Declaration}
\chapter*{Abstract}
\chapter*{Acknowledgments}
\listoffigures
\listoftables
\chapter*{List of Abbreviations}
\mainmatter
\chapter{INTRODUCTION}
\section{Motivation}
\section{Introduction to Data Mining}
\newpage
\section{Steps for Knowledge Discovery in Databases Process}
\section{Architecture of Data Mining System}
\newpage
\section{Datamining Techniques}
\newpage
\section{Classification}
\subsection{Naive Bayes}
\subsection{J48}
\newpage
\subsection{OneR}
\subsection{ZeroR}
\subsection{IBk (k nearest neighbor)}
\section{Association Techniques}
\section{Description of Heart disease dataset used in Experiment}
\end{document}
\documentclassand ending with\end{document}) that gives rise to the issue you're looking to fix. From the screenshot it would appear to be the case that you've customized the table of contents layout considerably -- in addition to providing an instruction that inserts "Chapter " before numbered and unnumbered "chapters". A solution to the "Chapter " business for unnumbered chapter-level entities will probably interact (interfere?!) with your other code, so it's important to know what you've done. – Mico May 09 '14 at 05:50