Bullshits? It's better to upgrade it to WINDOWS 7 idiot, vista's are very big and not very good for gamers like Gogo. So shut up and let gogo decide!!
Don't tell people things you know absolutely nothing about.
As Gogo is only experiencing problems in the multiplayer, the fault most likely is not in the operating system itself.
Formatting and re-installing your operating system only helps with faults inside the operating system,
not on separate issues concerning softwares or default settings.
Gogo, have you checked that your Firewall is not blocking SA:MP? Do you have the latest SA:MP in use? (0.3c) Just open the menu from the Start button, write Firewall to the search bar and choose the option to allow a program or feature to pass the firewall. When the menu pops open, make sure SA:MP is on the list allowed.
If that doesn't work, then the next step is to re-install your game and SA:MP. Uninstall SA:MP, then GTA SA. Remove all the game directories, including the ones at My Documents (GTA San Andreas User Files). Then install GTA SA again and the new SA:MP Client (0.3c). See if that helps, if not - report back here.