Sanjay, if your bitcoin client is not running, this does not mean your wallet is lost. Sometimes bitcoin client doesn't run for me either and I've got to manually close any previous executions before it will run(sometimes multiple times). If your wallet is missing, bitcoin.exe will still run. Check your "c:/users/(your account)/appdata/roaming/bitcoin/ " your wallet should be in there somewhere if it is still there.

Hope this helps.