Sometimes you may face the “Disk I/O error” message when attempting to sign in to Skype so to resolve this problem follow the below Instructions :
1.Make sure that you are using the latest version of Skype.
2.Quit Skype. If you can see the Skype icon in the task bar (at the bottom right of your screen), right-click it and select Quit. If you cannot see the Skype icon, use Task Manager to close Skype. Simply press Ctrl+Alt+Delete and click Start Task Manager. In the Applications tab, select Skype, then click End Task.
3.Click Start >> Control Panel. From the menu bar, select Tools > Folder Options….
4.Click the View tab.
5.Under Advanced settings, select Show hidden files, folders and drives, then click OK.
6.In Windows Explorer, navigate to: C:\Users\<your_windows_username>\AppData\Roaming\Skype (Where <your_windows_username> is your Windows user name).
7.Look for the folder with the same name as your Skype name and delete it. If you’re signing in with your Microsoft account, the folder will start with live#3.
This will delete your chat history. To save your chat history, open the above folder and copy the main.db file and the chatsync folder to another location. You will be able to transfer them back (described in step 8 below). Be aware that we cannot guarantee your entire chat history will be restored.
8.Restart Skype and sign in with your Skype name and password. If you forget your password, these instructions tell you what to do.
9.The folder you deleted in step 7 will be re-created. If you saved your chat history files (described in step 7), transfer them back into the folder with the same name as your Skype name.
Its done .. Then try to login to skype with the same Username and Password.