Hello,
Could provide us a brief explaination on when you say "it's not replaceing sylink.xml file on win7 machine's"?
Does it provide you an error message during replacing the sylink.xml on the client machine OR Sylinkreplacer is unable to detect the Windows 7 machines?
Check these Article:
When running the SylinkReplacer tool to replace the SyLink.xml of the SEP client the error "No SEP clients discovered" is reported
http://www.symantec.com/docs/TECH154680
What ports does SylinkReplacer for SEP use to communicate across the network?
http://www.symantec.com/docs/TECH186661
Secondly, SEP 12.1.2 (due to release soon) has a new feature: you will be able to connect existing Windows SEP clients via Client Deployment Wizard using the Communication Update Package Deployment option. This will work for both 11.x and 12.1.x clients. In other words, the Sylink Replacer functionality will be built in to the SEPM.
Check this Article in reference to the SEP 12.1 RU2 on this new feature:
http://www.symantec.com/docs/HOWTO81455
Hope that helps!!