Cannot find or parse web template file

I was trying to create a SharePoint site collection based on a template saved with lot of site level customizations. Site collection templates should be available in global template gallery and it can be added there using the Stsadm commands I tried to add the template in the global template gallery by using the following command

"stsadm -o addtemplate -filename "c:\mysitecollection" -title "Ari Site collection" "

But it was giving the following error

"Cannot find or parse web template file c:\mysitecollection."

It was a simple error to resolve. But was on a bad day and made me to sweat lot. Yes, the think i missed is the extension of the file name . I modified the command like below and it worked :( another bad day.

"stsadm -o addtemplate -filename "c:\mysitecollection.stp" -title "Ari Site collection" "