When I am trying to open .xls file save in the drive by double clicking it, the MS EXCEL application opens up but the file is not opened.

If I used open option in MS EXCEL then the files open up but not by double clicking it.

The problem is in some EXCEL there are excels attached as object so I am unable to open those also.

I tried uninstalling and then installing again but that too of no use.

check and make sure the option "Ignore other applications" is not checked in excel's options. I'm not sure exactly where it is because i don't know what version of excel you have but just find Options and look through till you find that option.

good luck

Generally found in:

TOOLS --> OPTIONS --> GENERAL TAB --> IGNORE OTHER APPLICATIONS

Regards,
Rollin