The Messenger app I use the most is Telegram mostly because it has clients for iOS, Windows Phone, the web and a Windows Desktop client which I still prefer when sitting at a PC.
I use the portable version which keeps the whole app confined to one directory in Windows
I found myself in a situation where I was away from home working an or third party PC for a while. I downloaded Telegram portable but during the first run it requires you to verify your account via an SMS message to your mobile phone.
I did bring my phone but both SIM cards do not work here (East Asia), so those SMS messages never reached me.
Being a portable app, I assumed the data files would contain my Telegram identity. So I VPNed into home and started my main PC to RDP into it. I then copied three of the Telegram files:
\Telegram\data \Telegram\data_config \Telegram\tdata\configinto my new Telegram directory. I then started the app and voila, it works
So sorry this only works if you already have a working Telegram Portable version.
When I tried this with Telegram Version 1.0.29, the files had completely changed, I now had to copy the following files:
Telegram\tdata\D877F783D5D3EF8C\map0 Telegram\tdata\D877F783D5D3EF8C0 Telegram\tdata\settings0 Telegram\tdata\usertag
I have no idea whether these names are always the same, but this worked for me.
I recommend using a local passcode if you are using the Portable Version on a USB drive