Hello,
There wouldn't be any impact when simply increasing virtual disk size.
Any idea what is using the highest disk space on your machine?
Check these Articles:
Disk space management for Endpoint Protection Manager
http://www.symantec.com/docs/TECH96214
Error: "Low Disk Space" on computers running Endpoint Protection
http://www.symantec.com/docs/TECH153952
How to free up disk space on a Symantec Endpoint Protection Manager server
http://www.symantec.com/docs/TECH163063
Regards,