Drivers

Maybe there is nothing wrong with the modem. Have you checked the phone line? Plug a regular telephone into the jack and make a call to be sure.

Okay, here's what to do.

1) Verify you have a dial tone on that line (plug a handset phone in and listen)

2) Go under your device manager under system in the control panels and delete the modem.

3) Reboot, when it detects the modem, direct the system to the required driver files (on CD, Floppy, wherever).

4) Open the device manager again and see if the modem has a question mark etc to show there is a problem.

5) If it looks okay, close that and go under the modems section in control panels.

6) Select the diagnostics tab and click on the modem.

7) Click more info to test the modem. If all is well, it will list a series of details. If it says the port is already open or some similar error, you most likely have an IRQ conflict with another piece of hardware on your system (a serial mouse or other serial device is the most likely culprit).

If at this point all looks well, check your software settings to dial you ISP...and then try to connect.

If you run into trouble going through these steps, make sure to post the details and we'll help further.

Good luck!

Gointo Control Panel, System, Device Manager and highlight your modem. Right-click on it and left-click on "Properties". You should see a tab which says "Driver". Click on that tab and Update driver. Use the driver you used before which worked.
If that doesn't sort it, remove the modem completely from Device Manager, reboot and reinstall it.

If it still doesnt work, my guess is a fault with the modem or the phone wire.

Since it has worked before we'll assume the line is comnnected to the jack that is for line on the modem. As someone said here connect a headset or phone to the other connector and see if there's a dial tone.

Can you hear a dial tone as the modem goes to connect? Is it originally a SINGLE SOLID tone or is it broken like when you have messages waiting.
I've ran into this situation a few times with some of my customers. If you have instant messeging on the phone line and if you have messages the phone will not have a solid tone the modem will not connect. Make sure to listen to and save or delete all message before trying to use the modem.

If we look at as a hardware, first it depends on which type of USR modem you have if it's a courier, win modem etc. As mentioned here, issues such as device conflict etc.

Courrier modems
From the desktop, right click on the my computer icon and select properties. Choose device manager. Delete the modem but do not restart. Open control panel and press add new hardware. Once this step is complete windows may only find a COM PORT this is good. Now restart the computer and the modem should come right up.

Winmodems

Again remove the modem.
When the device is removed, click the Refresh button.
Reinsert the installation disk at the prompt and continue the installation.

Note: You cannot install the Winmodem using the Add New Hardware option within the Control Panel or by clicking Start and then clicking Run.

Open up the casing and get the modem card unplugged and clean the contact pins by rubbing it with rubber pencil eraser, I think you have bad modem pins contact to the slot socket due to dirt and micro obstacles, sometimes the pins contact ok and sometimes not, that's why your modem works fine and another time it won't

Open up the casing and get the modem card unplugged and clean the contact pins by rubbing both sides with rubber pencil eraser, I think you have bad modem pins contact to the slot socket due to dirt and micro obstacles, sometimes the pins contact okand sometimes not, that's why your modem works fine and another time it won't

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