I only just bumped into this cool skype trick.
As you can see from the pic above, I'm running 3 skype accounts (on XP) at the same time. This can be handy if you want to open a very private (family, business, coaching) group without having to be "invisible" to (maybe many) others when it's not convenient to be bombarded with a trillion requests and well wishers.
Create a new shortcut (right click --> New --> Shortcut) and place this in the "Target:" line...
"C:\Program Files\Skype\Phone\Skype.exe" /secondary
It'll open a new skype with a new login screen and you can simply login with a new account. Once that's open you can click the same icon again and a third will open up. I don't know what the limit is but I was pretty surprised that after so many years I only just learned this cool tip. I hope it helps.
Edit/Added: From post 10 below...
Here's another little trick I just picked up and tested. I'm not only running multiple skype accounts at the same time on the same machine but now I'm also running Skype v3.8 (portable) which was the last awesome skype. In my opinion, apart from screen-share all versions from 4+ pretty much all sucked and now that Microsoft has taken over it's even worse.
For example, search and sort by country (essential when searching for someone's name) and private groups. 4+ signified the end to being able to properly control private (actually and ironically called "public") groups. It's still possible but it's all done by command line (type /help into a newly created group and marvel at the options).
The only problem is of course that everyone in your little private group has to also run a portable skype 3.8 install which is easy enough - just give them a zip file to extract and it'll be self contained. Make sure you delete your own personal folder from inside the new "Data" folder which will be created in there by Skype after your first log in.
To get skype v3.8 running on a machine alongside a newer version of skype you have to run a switch after the command called /portable and you need the skype v3.8 exe file (not the installer but the file the shortcut points to after you've installed v3.8). The portable command tells skype to use a local directory to store data instead of the registry. In other words, you...
- Create a special directory (e.g. skype38)
- Paste the skype 3.8 exe file into that directory,
- Create a data subdirectory directory, call it Data (or anything you like as long as you use the exact name in the command line)
- Create a shortcut to the 3.8 exe with the following command...
X = my USB data drive. Change it to suit your drive letter. Make sure you include the spaces exactly as it's written here.
You can even install skype on a portable thumb drive which will run on any windows machine but there's an issue with drive letters changing so you need a more complete (free) solution called "PortableSkype" which you can find here.
Tip: If you get an error message when you try to open it about skype currently running and asking you if you want to close it and open a "portable" version from a USB drive (the error I just got), close your current (latest version) skype, start a portable version then start a new "duplicate" version using the directions in the original thread post above.
Update from original post: A simpler way to run multiple skype accounts would be just add the /secondary switch to your original skype shortcut. To save you scrolling back up to the top, it's "C:\Program Files\Skype\Phone\Skype.exe" /secondary (including quotes and spaces).