Doubling Download Speed
 

This maybe be a lil far fetched.

when i usually download files, i get like 125 kbps speed.

the speed goes down when more files are being downloaded at the same time.

i have 2 pc's on a router-linked network.

so, is it possible to download part of the file on one pc and part on the other one??
then combine 'em both. (i get higher speeds across the network).

From what your describing it sounds like your modem is capped, at around 150k/s I doubt you would ever notice any speed increase if you were to D/L one file from one comp and one from teh other. A router doesn't give you 2 lines, just allows both comps to connect through the same one, so you shouldn't see better performance. However if you were to get a second IP address from your ISP then you should be able to set up ICS on one comp and Run it into your second and using that little feature where you can Bridge 2 connections in XP, you should in theory be able to double your speed, that is if its not the server your downloading from holding you back.

If you modem is capped, you will only be able to download as fast as that cap allows +/- a few %.

Using a download manager such as Download Accelerator Plus, will help keep your downloads coming as fast as the server allows you to download, and the as fast as the cap on your end.