Hi sofian33,
If it is a wireless card and you are comfortable opening the system chassis, you can try re-seating the card and see if the issue persists. You can find detailed information on re-seating wireless card from link:
ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_vostro_desktop/vostro-460_Owner%27s%20Manual_en-us.pdf
Note: Please ensure to follow safety instructions mentioned in manual.
If it is an Ethernet card, it is integrated on motherboard of computer and might need replacement. Another possible option in this case can be to use a PCI or USB network card, which would workout cheaper than replacing motherboard.
If the system is under warranty, you can private message me the Service Tag of computer. I have added you as a friend. Please accept my friend request by clicking on my name highlighted in blue and then click on “Friends” tab at the top and then click on “Request to Review” and finally click on “Accept” button.
I am sending you a private message as well. Click on “Inbox” to respond to the message and provide system’s Service Tag and contact details so I may access your system records and check for further course of action. You could also click on Start Conversation to send a private message.
Please reply for further clarifications.