Below you will find 2 options to add wireless connectivity to your desktop.
A. USB Wireless LAN
This is the easiest solution to add a wireless connection. Simply connect the USB adapter, install the software it comes with and connect to the wifi signal, once configured.
B. PCI/PCI-e Hardware Wireless LAN
Adding a PCi/PCI-e expansion card requires opening your computer and manually installing the card, then installing the driver/software and configuring the wireless access. These cards typically offer faster speeds and stronger radios to communicate with wifi signals better.
NOTE: There are 2 types of wireless cards in the second link: PCI/PCI-e and Half-Card/Mini-Card. Half/Mini-Card adapters are for laptops only - they will not work on desktop computers!
Both USB or PCI/PCI-e offer excellent solutions to getting wireless access from your desktop. Furthermore, since it can be purchased through Dell.com, they can ship anywhere worldwide, so delivery to the Netherlands should not be a problem.
If you have any questions, you can always contact Dell's Customer Support by telephone and be sure to give them your service tag number, that will ensure that you get only the parts that match your desktop.