There might be some considerations:
Possible 802.11Compatiblity Issues
Your Dell Inspiron N5110 is a 802.11b/g/n (2.4GHz and 5GHz) capable notebook.
You Nokia-C5 (specifications) is a Wi-Fi 802.11 b/g (2.4GHz).
For them to work together make sure the that the Dell Inspiron is not using the 5GHz-only band mode. If you set it to be 802.11b/g compatible (combo) it will be enough (I think the "b/g combo" mode might be the default value on any 802.11n).
Your Dell D865 PC, you specify on the comments you use a Wi-Fi USB-dongle in 802.11a mode (5Ghz).
That's an issue.
With your 802.11n card you can set it to 5GHz ONLY mode. So 802.11n it will be 802.11a compatible, and you will have connection between them.
BUT if you do so your Nokia cellphone (2.4GHz) won't work.
First check if your USB dongle has 802.11b/g/n capabilities, if so, go to that mode (2.4 GHz).
Otherwise, if the USB dongle is 802.11a-only, The only solution (cheaper) for using the cellphone and the other notebook together will be buying a new USB Wi-Fi dongle with at least 802.11b compatibility.
With your current devices you will never be able to use your 802.11a computer and your 802.11b/g cellphone on the same Wi-Fi Network as those technologies are not compatible.
Possible problems in ad hoc network mode on Win7
Can you please explain which method did you use to convert your laptop into a "router"?
The fast solution to share your laptop's internet connection through Wi-Fi will be creating an Wi-Fi ad hoc network, on windows 7 you can follow this tutorial for doing so.
IF an ad hoc network is the the solution you are using to convert your laptop into a "router", and you cannot find the network on the other notebook even if you are close to the network (try to be close!) -and make sure about the compatibility issue I mention later-, then, the problem most probably is a scanning (802.11 MAC) issue and not a physical ("not enough signal" or compatibility issue) one.
So to find a solution in this scenario try to:
- Manually define the Wi-Fi network ("add network") on the other notebook and define the same Wi-Fi network name you set for the ad hoc network.
This way the scanning of the environment will specifically "ask" for your network name, and the windows 7 notebook on ad hoc mode will "hopefully" respond to that specific scan question (you will make it "visible").
In a more generic way (I'm not familiarized with the windows7 automatic ad hoc), normally you can find standard wireless networks because the wireless access points actively announce themselves (they broadcast beacons). An ad hoc network does not require this. So to be sure you "find" it you have to actively scan for the ad hoc specific network name you set.
IF you are effectively associated/connected to the Wi-Fi ad hoc network, but Internet does not work, then:
- Check what IPs you have assigned on both sides.
- On the windows side, make sure you have "shared" (by tunnelling) your (USB) internet connection to the Wi-Fi interface.
I think both issues should be handled automatically if you are using the default Windows 7 ad hoc network solution.
Please add more information about the way you are trying to share your internet through Wi-Fi, so we will be able to help.