How to setup a wireless LAN ?

I currently have a desktop computer running windows 7 and a lapptop running Mac OS X 10.5.8. My wifi router is Tenda 311R b/g/n 150 Mb/s. Can you show me the way to setup a wireless lan?

I tried to set the shared folder on windows7 but, how to say it .... both my desktop and lapptop (running OS X) cannot see each other. I can only access to shared folder when my lapptop also running W7, and the speed connection is very low (only about 5 Mb/s )

Thank you for your helps.

DIY: Add a Mac to your Windows Network - PC & Desktop Computers

Accessing Mac and windows 7 on same network - Mac Forums

Windows 7 and Mac OS X Sharing

*Edit*

After follow all the instructions, my PC can access to the Mac but the revesce is not ) :

Were you able to successfully make the edits to regarding NTLMv2 and 128bit encryption on the windows 7 machine that are referenced in cybercore's second link.
Are you receiving any type of errors when you attempt to access the Win7 machine, (access denied, network path not found, etc)?
Can you see the Win7 machine from the Mac?
Can you ping the Win7 machine from the Mac?
Uninstall any third party security software from the Windows 7 machine (Zone Alarm, Comodo, Nortons, McAfee, etc.) just to make sure that they are not the issue. You can always reinstall later.
Temporarily turn off the Windows firewall for testing.

Were you able to successfully make the edits to regarding NTLMv2 and 128bit encryption on the windows 7 machine that are referenced in cybercore's second link.

Yes, I can.
I am able to ping the desktop's ip.
I'm currently using Kaspersky antivirus. After uninstall it, I can access to the W7's shared folder ... so the problem's solved. Maybe I'll find another AV software

It's weird that now I cannot turn windows firewall on ? "The action center can't turn on windows firewall", when I tried turn it on manually, it's just have a "used recommend settings" option, but nothing happend afterward ...

The first thing I would recommend doing is reading this article, download the appropriate uninstall tool direct from Kaspersky and make sure all remnants of all former antivirus programs are gone. http://support.kaspersky.com/faq/?qid=208279463
Then download and install Microsoft Security Essentials. http://www.microsoft.com/security_essentials/
If you are still having trouble with the windows firewall after this post back and we'll see if anyone has more ideas.

I did what you said but still cannot turn on windows firewall though.