Weird how you just drag something to the trash can to delete instead of going thro the whole process of uninstalling a programme !
That one isn't strictly true I'm afraid, there are some applications you can do that for just like there are some you do it for in Windows, but many will leave behind a load of junk in preferences and shared areas unless you run the uninstaller
To answer a some of your earlier questions.
I work in a mixed environment of both Macs and PCs and have done for about 20 years.
Things I miss about the Windows PC when I'm on the Mac:
1. A delete key! I know I can use fn backspace, but it's not the same
2. Reliability (this one will get me hate mail), but I have to say that for me, my Windows 7 systems are much more reliable than the Macs (as Was XP and NT4 - the less said about Windows 2000 and Vista the better)
3. The task bar - you already mentioned it, but there isn't a convenient equivalent of the Windows task bar
Things I like about the Macs:
1. They look really nice
2. They've got a UNIX based OS, so I can use lots of the command line stuff I used to use in HP-UX and SCO UNIX years ago
3. They are less likely to suffer security attacks (though see below)
One thing I hate about my Mac laptop - the stupid shiny screen which makes it virtually useless in bright sunlight; a portable computer than you can't use outdoors seems ridiculous. I'm just annoyed that I didn't realise it before I bought it, especially as I remember having to go round installing matt finish anti-glare screens over the top of shiny PC monitors about 25 years ago. As far as I'm concerned that's a real retrograde step in design and I can't believe that many PC manufacturers are now following suit.
You asked about using security products. I would say definitely yes and so do the specialist security consultants I work with. Modern endpoint protection products from the likes of Symantec and McAfee are relatively cheap and are no longer the intrusive resource hogs they used to be.
There is no such thing as an invulnerable OS, both OS X and Windows have had and continue to have serious holes, these are patched up whenever found and both vendors are doing good stuff to make it harder for those with nefarious intent, but both are at risk. The thing that makes Windows more vulnerable is not the OS itself, but simply the fact that there are so many more people attacking it than are attacking OS X, however, the attackers are targeting OS X more and more frequently and are increasingly aware of the untapped market for them.
If you think about it from the attacker's point of view, then assuming both systems are equally difficult to break into (and there's some debate about that because Mac users tend to be more prone to the social engineering type attacks as they're not used to them like PC users are). If Macs are 10% of the market but 90% unprotected and PCs are 90% of the market but 10% unprotected, then the overall attack surface is identical for both. It's up to you, but I would put some kind of security product on any Internet facing system that I cared about, especially if I was planning to do things like enter my credit-card numbers on it, the risk may be small, but I don't want to find out the hard way that there is a trojan installed on my Mac.
----------
Where do I look to see all the programmes downloaded onto the mba ?
ie: Ive downloaded u torrent.
Where do i go to see the downloaded programme.
In Finder, under Places, click on your username and you should see a folder called downloads
I feel we are somewhat lucky, we can enjoy Lion without trying to hold onto "the good old days" with how things used to work. 
Mac !
