I have a new computer wireless and like to install my brother MFC 8870DW,I have lost the CD to install

first, Enable the WIFI on you printer, then install the driver in you computer, to option to choose before you finish the installation, First Select your connection, Choose Wireless Connection, not USB Cable

There are shorter way but are machine dependent, this will work for all...
http://tricks-collections.com/reset-all-models-of-brother-printers/

How do I connect a Brother MFC 7840W printer to a Bell Network. Every time I try to connect, I get a connection NG message on the printer. Any help would be greatly appreciated

Connect the printer with a USB cord to the computer. Switch off the printer and install the driver in to your computer , during installation the software will tell you to switch-on the . Do so and finish the installation .
This is the procedure to connect the printer with your computer.

Remove and reinstall the cardtridge.
Check manual for new cardtridge code (if needed).

You must reinstall the software on the computer to which the printer is physically connected. i think u are using usb to connect to computer so to share it out u most buy printserver or use let the computer where its physically connected just to be on and u share there the computer to your workgroup computers

With in 2 seconds you have to hit Menu,*,2,8,6,4
Continue even though you hear the 3 beeps.
When it does into maint mode press 88
That is parts counter reset
Scroll to the part and hit ok.
Press 99 to exit Maint mode

23/Feb/ 07: Updated the Brother original driver(Full Driver & Software Package) for the following products to fix a driver installation problem: FAX-2820, FAX-2920, DCP-7020, DCP-8060, DCP-8065DN, MFC-7220, MFC-7225N, MFC-7420 ,MFC-7820N, MFC-8460N, MFC-8660DN, MFC-8860DN, MFC-8870DW, MFC-9420C 

And here is the link of the updated full driver and software package. After you download this, you should be able to run the MFC 7820 with your new laptop=)

well..I suppose we should determine that you have your small office/business network set up first, right? it's under network connections. If it's not there, then your printer will stay invisible. Is this a replacement or new install?

You can try searching the web for the driver for that machine or call Brother directly at 1-800-284-4357 and order another cd

John