Macbook MSN account hacked

[MrHappy]

Probably the most weird problem I have had, I was talking to a friend on msn when suddenly someone else on my contact list sends me a link called piccy.com/something/something/tianxiong/something.com (Tianxiong is my "English" name) with the message "hey its you!" I clicked it, thinking its just some picture that I put on facebook, which these days end up on Google images somehow. It was a Chinese website that asked me to sign in with my windows live ID (I was stupid enough to trust random Chinese web pages) so I did. After I did, the site started loading, and loading, and loading...etc...etc. I didn't think it was of much importance so I closed it, but one day my parents bust in my room and say I send them a link at 5am, that I didn't really send. A few days later my friend received the same type of thing, something like "Find a love life today at ......whatever...." So later I left my laptop outside for the night and the next morning both my parents received messages link to "adult" websites. Then I knew I had been bugged or something, so I tried to change my password, but I couldn't change it or log in to anything related to msn and random contacts kept getting random websites. I managed to change my password on another computer, but this one remains "bugged" and its so annoying and now I can't even access certain antivirus download pages such as norton antivirus from softpedia.com. Somebody help please?

(I am using a Macbook with Mac OS X version 10.5.6 silver model, 2 GHz Intel Core 2 Duo processor, memory: 2 GB 1067 MHz DDR3)

Complete description:Hardware Overview:

Model Name: MacBook
Model Identifier: MacBook5,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 3 MB
Memory: 2 GB
Bus Speed: 1.07 GHz
Boot ROM Version: MB51.0073.B06
SMC Version: 1.32f8
Serial Number: W8903QET1AQ
Sudden Motion Sensor:
State: Enabled
Please help me, this is a rented computer from the school!

 

[kimsland]

Read: Is your system infected? Read this before Cleaning or Formatting

That's the only thing I'd be doing

 

[DelJo63]

this is called Social Engineered Virus' -- you just can't trust this stuff as you now understand.

Try to download ClamXav from here

If you can then

1. disconnect from the internet
2. perform the install

can you handle the OS X install?