I have a D-Link DGL 4500 wireless router. I have

If the default password on the D-Link has been changed then-
To reset the D-Link back to the default settings -
Press and hold the RESET button at the back of the router with the power ONuntil the LEDs flash at the time the release the RESET button.
Connect a LAN cable from the D-Link to your laptop/computer's LAN port, openthe browser on your laptop/computer and enter the D-Link's configuration URL..
http://192.168.0.1
The default login = admin
The default PW = blank (just press Enter) You can now change the default admin password.
You can now configure the wireless settings. Now configure the wireless card in your computer/laptop withthe router's wireless settings.
To secure your wireless network from unauthorized access,please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

To get into the D-Link DGL 4500 router homepage, simply open an internet browser window and type in the following address:

http://192.168.0.1 and press Enter.
When the login window appears, set the user name to Admin and leave the password box empty.
Then, click Login to continue.

Here is the link to the PDF version of the User Manual:
http://www.dlink.com/-/media/Consumer_Products/DGL/DGL%204500/Manual/DGL%204500_Manual_EN_US.pdf

Make sure you have the latest firmware as this might help with your dropped connections. Also try to make a DHCP Reservation for each computer connected to your network (p. 32 in the User Manual), as that can also help prevent dropped connections.

Download the latest firmware ver. 1.23NA to your local computer. Connect your DGL-4500 router via a wired connection (ethernet) to your computer and install the firmware update following instructions in the user manual.

Firmware link:
ftp://ftp.dlink.com/Gateway/dgl4500/firmware/dgl4500_FW_123NA.zip

Here is the PDF link to the User Manual:
http://www.dlink.com/-/media/Consumer_Products/DGL/DGL%204500/Manual/DGL%204500_Manual_EN_US.pdf

go to D-Link - TechSupport FAQ, they have a tool to help configure routers,

You will need to check the wireless settings of the router
is there any computer connected to the router ?
If yes then you can open the router set up page on that computer.
Router set up page is the page where you can check all the wireless settings of the router.
Click here for step by step instructions

i think its working.Connect the ethernet port of moden to wlan of wireless

1. I assume you downloaded the newest firmware (version 1.21NA) from this site.
2. Save or move it on your desktop so it's easier to find.
   
3. Connect your router to your computer with an Ethernet cable.(If you're not sure what it looks like, see here.)
   

Do not upgrade the firmware over a wireless connection!

On the same page, look at the FAQ's. there is an entry called "How do I upgrade the firmware on my DGL-4100/DGL-4300/DGL-4500?" It is a description of the upgrade process itself and will walk you through the steps.

I'm just amazed that they miss a really important warning. Do not unplug your router or close the browser on your computer until this process is finished. This can render your router useless and you will have a nice, expensive doorstop.
When the upgrade process starts, go have a coffee, do your dishes, whatever, but: Leave the router and your computer alone! Wait until the router's reboot is completely finished.

If you have any more questions, just come back here and leave a comment - I'm happy to help.

No need to reset the password, if you know how to login to the router you can check there the security that you needed to be able to connect wirelessly.

make sure the dsl modem is in bridge mode. you do this by connecting directly to the modem then accessing modem configuration page. after doing this connect the way everything was before. now go to router admin page, then setup tab at the top, then choose internet, manual setup. in the place where its says my internet connection is select PPPoE. then put in your dsl username, password and etc. save settings. this should fix the problem

This can be a firmware problem so upgrading the firmware of the router should fix this issue on it, so I advice you to upgrade to the latest firmware of your router, you can get it from Dlink web site...