On this forum I see there are a lot of questions about installing WIFI using ndiswrapper, I have figured it out and I want to share it with you all. I made a howto in which I have combined all the solutions I have found. This is the system I use:

HP Pavilion zv5133ea
AMD64 3000+ met 512 Mb intern
Nvidia GeForce4 440 Go 64M
Broadcom 802.11b Wlan
Realtek RTL8139 NIC
Ubuntu Hoary Hedgedog 5.04 64Bit / WinXp dual boot

The first problem I have encountered was that the ndiswrapper-1.1 version didn't work. My drivers were installed however the command iwlist did't show any APs, the solution I found was to install the newest version of ndiswrapper: Ndiswrapper-1.2-RC1 .

The next step is to get drivers, I'm working with 64 Bit Ubuntu so I need 64 Bit drivers, here is a link to get windows wlan drivers for most Wlan cards: Wlan drivers . This link provides also 64 bit drivers for all broadcom cards.

Ok, on to the installation:

Step 1: Remove the old ndiswrapper and all links to it's driver.
sudo modprobe -r bcmwl5 
sudo rmmod ndiswrapper 
sudo apt-get remove ndiswrapper-utils 
sudo rm -r /etc/ndiswrapper/ 
sudo rm -r /etc/modprobe.d/ndiswrapper
Step 2: Install Linux-headers.

sudo apt-get install linux-headers-2.6.10 (enter your version of linux headers or usr the synaptic package manager)
Step 3: Install Ndiswrapper.

cd /home/username/ 
sudo tar xvzf ndiswrapper-1.2-rc1 
cd /home/username/ndiswrapper-1.2-rc1/ 
sudo make 
sudo make install
Step 4: Load drivers with ndiswrapper.

cd /the_dir_you_put_the_wlan_drivers_into/ 
sudo ndiswrapper -i bcmwl5.inf (fill out your own drivers for bcmwl5.inf) 
sudo ndiswrapper -l (shows if the driver is installed)
Step 5: Load ndiswrapper and check if it worked.

sudo modprobe ndiswrapper 
sudo dmesg (shows that the card is installed (hopefully)) 
sudo iwlist wlan0 scan (shows all APs surrounding you)
Step 6: Make sure Ndiswrapper is loaded during bootup.

sudo ndiswrapper -m
Step 7: Configure your Wlan card.

sudo iwconfig wlan0 essid name_of_AP (the name you found by using iwlist wlan0 scan) 
iwconfig wlan0 enc <key> (fill out your WEP key (if you have one)) 
sudo dhclient wlan0 (gets a dynamic IP adress) 
sudo ping -c 3 www.ubuntu-linux.nl (tests the connection)
Step 8: If you are using WPA encryprion check this thread WPA encryption voor Ndiswrapper .

I hope this will help some people. If there are comments or extra info you have please add it to this thread, it could help somebody.

Greets Hieronymus