Because the stuff you've posted isn't complete it's impossible to work out what's really going wrong. What you need to do therefore is to strip this down to a MINIMAL but COMPLETE set of files then post the filename and COMPLETE file contents, then we stand a chance of working out what is up.

So for example I've got the following code:
thread46040.cpp:
Code:
// thread46040.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "tree_stack.c"
#include "check_stack.c"

int _tmain(int argc, _TCHAR* argv[])
{
	display_stack();
	return 0;
}
tree_stack.c:
Code:
extern struct node* nd;
struct node
{
int element;
struct node* next;
};

void display_stack()
{
struct st* curr;
// while(....)
printf("%d",curr->nd->element); // here its showing error

return;
}
and check_stack.c:
Code:
struct st
{
struct node* nd;
struct st* nxt;
}
and I'm getting various errors:
Code:
1>------ Build started: Project: thread46040, Configuration: Debug Win32 ------
1>Compiling...
1>thread46040.cpp
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\tree_stack.c(12) : error C2027: use of undefined type 'display_stack::st'
1>        c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\tree_stack.c(10) : see declaration of 'display_stack::st'
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\tree_stack.c(12) : error C2227: left of '->nd' must point to class/struct/union/generic type
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\tree_stack.c(12) : error C2227: left of '->element' must point to class/struct/union/generic type
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\thread46040.cpp(8) : error C2628: 'st' followed by 'int' is illegal (did you forget a ';'?)
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\thread46040.cpp(9) : error C3874: return type of 'wmain' should be 'int' instead of 'st'
1>c:\documents and settings\dave\my documents\visual studio 2008\projects\go4e\thread46040\thread46040.cpp(11) : error C2440: 'return' : cannot convert from 'int' to 'st'
1>        No constructor could take the source type, or constructor overload resolution was ambiguous
but I have no way of knowing if any of these correspond to any of the errors you're getting.

Both me and asadullah have now tried - and failed - to construct your code from the sparse descriptions you have given, so I think it's only fair now that you realise you must strip (an experimental copy of, if necessary) the program down to the bare minimum and show us exactly what is going wrong.

Also you need to post the EXACT errors, like I have done above. It's no use saying vague stuff like "error of smth like "accessing incomplete data "" and "here its showing error" - these could both mean absolutely anything and give no clue at all as to what is wrong.