Seen this error a few times and most of the people recommend you disable it. a False Alert.
This is more of a recommendation than a warning. More for when you are going to use memory dump for troubleshooting or debugging.
The SharePoint Health Analyzer detected a condition requiring your attention. Drives are at risk of running out of free space.
Available drive space is less than five times the value of physical memory. This is dangerous because it does not provide enough room for a full memory dump with continued operation. It also could cause problems with the Virtual Memory swap file:
Here is how to disable this warning:
in Central Admin open Monitoring and then Review rule definitions
Find the rule "Drives are at risk of running out of free space"
Edit it and remove the Enabled check box