connection for informatica failing in DAC

when I check connection for informatica thro' DAC I get following
error
- Connection failed
- please whether you created INFA_DOMAINS_FILE environmental variable
(system variable) with value
Variable value: \domains.infa
The path should include the name of the file. For example,
'D:\Informatica\PowerCenter8.1.1\domains.infa'.
- check whether informatica client and server installation path is available in environmental vairiable. If not, add them in instance config file and reboot server