Earlier I have provided links for downloading standalone version of latest Yahoo Messenger. Many of us prefer not installing app, instead run the application directly without any setup or installation. Yahoo does not have official portable version, but here is a version which can be run directly after uncompressing. You can carry this anywhere on USB flash drive and run from the device.
This doesn’t have any virus. But, please run a online free virus and malware scan at virustotal.com
After Uncompressing, just go to the directory and run the YahooMessenger executable.