Dll Problem

When I turn the sys. on it says I should run chkdsk utility. When I try to do this it says it is in a read only mode. You cannot get it to a point to run that program because when you reboot sys. it locks before it gets through the steps of the program. From a cmd I ran sfc /scannow, it went through the scan a said I have a dll cache error problem. tells me to insert your windows xp professional cd2 now . The problem is when I purchased the computer new it had all the software loaded and I did not get disc with it. How can I resolve this issue. If I escape out of chkdsk I can bring the sys. up and it works fine.If the sys. is turned off you go through the whole situation again, any ideas?