xdata struct WindowList{ 
struct Windows * thisW; 
struct WindowList * NextWindow; 

}; 
xdata struct WindowList temp; 
temp=temp.NextWindow;//this line is generating an error.'=' incompatible operand 

sorry while typeing i miss NextWindow. I have correct it in the above code. Ofcourse if it is Next in my code the error will not be the same.
i have also tried

temp=*temp.NextWindow

In the above case the error is the same as '=' incompatable operand.
If i do it like this

xdata struct WindowList * temp;
temp=temp->NextWindow;

In this problem is that temp is a pointer who is in xdata and pointing in to data. when this line is executed

temp=temp->NextWindow;

If the address of NextWindow is X:0x000300 the value assigned to temp after the above line of code is C:0x0300.
I haven't find any thing wrong in cross posting in this way u got answer quickly.
Regards
Farhan