Ethernet over unused twisted pair?

[scott-DPNOqEs/LNQ at public.gmane.org (Scott R. Ehrlich)]

I'm trying to find a way to get an Ethernet connection from a second floor 
room diagonally across the house to the first floor.    There is no plenum 
- no dropped ceiling, and having an electrician do the wiring is too 
expensive.

I _could_ go wireless, but I'd much rather pursue a hardwired option 
first.

So, it occurred to me that DSL is Ethernet than works over a pair of phone 
wire.   Is there any device that could convert the Ethernet signal from my 
Linksys box to something I could plug into a phone jack that is wired with 
the unused phone pair, then run a mating device in first floor's 
corresponding phone jack and get my hardwired network run that way?

Could using two DSL boxes on the wire do the job?

Other than an electrician and wireless, what are my options (other than 
do it yourself or don't do it at all)?

Thanks.

Scott