Do yourself a favour and find out what your ADSL stats are (line attenuation, SNR/noise margin, line speed - both for upstream & downstream) and post them here. Also tell us what brand & model ADSL modem you have.
Secondly, do a trace route to like www.google.co.za and post the results here too.
To do a trace route, open up Command Prompt and run: tracert www.google.co.za
You can right-click, mark and select all the text, right-click again and paste it in your post.