having two comcast modems?

[froggy_newb]

ok to get things straight, i do have comcast as my ISP, but, the comcast cable modem is all the way in my upstairs, so im using wireless with my sister right now, because we dont want long ass ethernet cords running through the house. so im wondering, i have this extra comcast modem (the blue box where you put in the cable cord and out comes the ethernet cord to get cable internet) and i want to use my long cable cord and run it from a cable jack into my room and then run a ethernet cord into my comp for 100mbps inty?

brief explanation:

materials i have:
long cable cord (1)
short cable cord (3)
cable cord Y splitter (2)
comcast internet blue box thingy (1)
semi long ethernet cord (1)
ISP i use is comcast

from the cable cord that goes into my TV> use Y splitter> long cable cord go to my room> connect to the comcast cable modem> semi long ethernet cord out from the comcast blue box thing to my computer.

would this work>? im trying it and i dont have any connection...did i do something wrong? do i need a special cable jack to get the comcast internet?

[PrntRhd]

Nope it won't work because Comcast is smarter than all that. They check your modem MAC address and serial number when installing HSI onto their system. If you try to use an additional modem they will almost certainly investigate.

[Erik]

I know my ISP will allow this, for an extra fee of course. If you are that interested in it you might want to just look into that.

But what is wrong with sharing the internet wirelessly? I mean you are probably getting speeds of like 5MBps, which is slower than any wireless technology so you should still be getting the full bandwidth. If there is some other problem maybe you should just look at fixing that.

Why would you run a long coax cable to run a second modem, but not an equally long CAT 5 to just have a wired connection? I don't really see any difference unless you already have the coax running nearby your PC.