Normally, we can login to use Skype account or Yahoo Messenger only one in a PC. However, there are still available ways to help us in using two Skype acounts as well as two Yahoo Messenger accounts in the same pc.
Below are the methods to do such things.
I. Run Two Skype Accounts.
In this tip, the requirements are Skype versiont 4.0 or later and two skype accounts.
1. First, login to your first skype account.
2. Look for the folder named Phone by going into the location where the Skype application has been installed. For example: C:\Program Files\Skype\Phone. In the folder “Phone“, you’ll see file Skype.exe. Here, we need to create its shortcut which will be placed at Desktop. Right click on the file Skype.exe and choose Send to –> Desktop (create shortcut). See the figure below.

Figure 1. Create shortcut to Skype.exe
3. With the recently created shortcut on Desktop, Right click on it and then choose properties (Figure 2).

Figure 2. Right click on the shortcut
Then we will see a properties window open as shown in figure 3.

Figure 3. Properities window of the shortcut
Next, we need to type a space continued by “/secondary” to the target section, see figure 4, and click Apply –> OK to close the window.

Figure 4. Add a space and "/secondary" to the section Target of the properties window
4. Finally, double click on the recently shortcut of Skype and then another instance of Skype will run. Now we are able to use two skype instaces at the same time and in the same pc. Enjoy!!!!

Figure 4. Two Skypes are running in the same PC
II. Run two Yahoo Messengers
In order to run two instances of yahoo messenger, we need to work with Registry of the window. The way we will do here can be called as registry hack.
1. Go to Start –> Run, type “Regedit“, and then click OK to launch Registry editor of the window (See figure 1).

Figure 1. How to launch Registry Editor
2. Navigate to HKEY_CURRENT_USER –> Software –> Yahoo –> Pager –> Test.
3. Right click on any free space and do as illustrated in the figure below.

Figure 2. Create New Registry Key
4. Rename as “ Plural“, see figure 3, to the recently created Registry Key.

Figure 3. Rename the Registry Key
5. Double click on Plural and give the value 1 to Value data as in the figure below.

Figure 4. Give value 1 to Value data
6. Finally, launch yahoo twice, then we will see the two login screens appear for us to login. If we launch it multi times, then multi login screens will launch. It means that we can use multiple yahoo messengers in the same PC (not only two).
Enjoy!!!!