cannot open files directly from winrar but can extract

We have been facing these problems in two of our computers with OS xp.

When we open any files in the winrar with double click, it opens any other files not in the winrar window.

For e.g. I have four pdf files compressed in rar format. When I open the rar and double click any one of the files inside, it opens an excel file in my desktop.

However if I extract the four pdf files anywhere and open it, it works fine.