InfoPath Dev

when i open a file in the infopath 2007 show error message below:

"this form was signed an expired or revoked certificate . since you are running under high security level the form cannot be opened.  "

i dont know how i can solve this .

please help me.

Hi

Can you once check the expiration date of Signature certifcate that is used for signing the form? 

I dont know how i can check

1.Start->Run
2.Type 'certmgr.msc'
3.click ok
4.Result:Certmgr window will open
5.Select Personal and Expand Personal
6.Select Certificate
7.User digital certicate detail will display in the right pane
8.Check the Expiration Date