Windows XP - How do I verify an installer package in Windows XP?

Hello

I am trying to install some smartphone desktop software on this PC, Windows XP, and it is coming up with this message;



Can anyone advise how I verify the installer package on this machine?  I checked the certificates for the file and it says that one of the countersignatures is not valid - however it works on other PCs?

Peter

Refer BlackBerry FAQ from here :

http://btsc.webapps.blackberry.com/btsc/viewdocument.do;jsessionid=9F0405DB9497F744D12A88EC67B33FEA?externalId=KB28396&sliceId=2&cmd=displayKC&docType=kc&noCount=true&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl