While I am trying to open multiple excel files system is saying no sufficient memory to do this operation and excel is getting closed. Please help

Try closing all Office apps, then navigating to:
C:\Users\%Username%\AppData\Local\Temp
and deleting everything in that folder. You might also try repairing the Office installation (via Windows Control Panel > Programs > Programs & Features > Microsoft Office (version) > Change > Repair).

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]