problem migt be that, if you are uploading something just close it or cancel it first then try the download again. if you are downloading it from download.com cable should have at atleast 500kb/sec. download only using your dell/fast one then see what happen. if it still slow try TuneUp Utilities(search it in google) and fix the registry. if you are using sp2, that's might be an issue with sp2, i have using sp2 before it's crappy!!! i upgraded from sp1 and i have Roxio GoBack so i could go back to sp1(very fast, and good enogh). even i donwloaded and installed the updates for sp2 patches internet still slow. so try no sp2. if it comes installed on your machine OEMedy then what i suggest is get the files you want from the hard drive back it up (before formating i suggest another router, since i don't know much about d-link, but 2 of my friends uses Linksys router with/without wireless got the speed they wanted with ~ 3 comps, model Linksys BEFSR41) then format(quick format, i used) it and install xp home or pro WITHOUT SP2!!!. Then youcould donwload sp1/sp1a from microsoft and stick on that that would help much.
as long that's what i did for my slow internet connection and it comes up no problem. off course i fix my registry alot and defreag it alot. Dell dimension 8200 1.8ghz,512rdram 410MAxtor 7200rpm 8mb buffer
Verizon Dsl 1.5mb/ mines 180kb/sec and by the way router i use is from verizon with 1 year committment VERY VERY GOOD ROUTER FROM WESTELL (VersaLInk, retail cost~$150 i got it free with one year committment with verizon.lol
enjoy and if you have problem regarding how to format xp, first of all don't ask me becasue i'm not a expert,but you can start a new thread asking how to do it.