"Procure ser um homem de valor, em vez de ser um homem de sucesso" - Einstein

Guia Rápido para configuração Sapo Voip:

configurações:

SIP Port: 5060
Proxy: voip.sapo.pt
Outbound Proxy: proxy.voip.sapo.pt:5070
User ID: +351xxxxxxxxx
Password: a_password_escolhida_na_area_de_cliente
Use Auth ID: Yes
Auth ID: +351xxxxxxxxx
Use Outbound Proxy: Yes
Use OB Proxy In Dialog: Yes

Quando temos problemas com ficheiros do sistema operativo utilizamos o System File Checker (SFC), que pesquisa, encontra e substitui ficheiros que estão em falta.

Scan, Find, and Replace Missing System Files

The System File Checker (SFC) can be used at a command prompt to scan protected system files and replace any files that are missing. Missing system files can be the cause of various problems, including startup and shutdown problems, and .dll errors. If you're receiving errors relating to protected system files, this utility might just solve the dilemma.

http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/ballew_commandline.mspx

Bem depois de tentar várias soluções para conseguir entrar no Windows Live Messenger arranjei uma que funcionou:

4.a. Click Start, click All Programs, click Accessories, and then right-click Command Prompt and choose Run as administrator. 
4.b. Click Continue when Windows requests permission to continue. 
4.c. At the command prompt, type the following command, and then press ENTER: netsh interface tcp set global autotuninglevel=disabled 

Note: This command disables the Window Auto Tuning feature.

4.d. After you disable the Auto Tuning Networking feature, verify if you are able to sign into Messenger.

Oo, my system won't boot !
-Boot up the PC from your Windows installation disk
-Select the "Repair your computer" option
-Select "Command Prompt"
-Input "bootsect.exe /nt60 SYS /force" (Without quotes)
-Restart the PC