Slow connection speed (after upgrading to SP3?)

Hey, recently my internet connection speed has gotten really slow for some unknown reason. It only affects this one computer I'm currently typing from, my two other computers are working completely normal. This one is a Windows XP SP3 machine, other two are Debian Linux and Windows XP SP2.

Soon after upgrading to SP3 I've noticed that I can't download anything from the internet very fast. Let's say I take a random file somewhere and try downloading it on all the three machines (not at the same time of course), my other Windows machine and Linux machine both get a good speed, let's say 500 kB/s for now. This SP3 machine is only getting like 80 kB/s though and from some servers it's even worse. The maximum I'm getting from youtube for example is around 20 kB/s while I can get around 300 kB/s with my two other computers. My internet connection speed should be 10M/10M but it's usually more like 5/5, that's not the point anyways.

I'm not 100% sure if it's SP3 causing the problems but I've tried with different browsers (Opera, Firefox, even IE) and it doesn't seem to depend on that. I don't want to upgrade my other windows computer to SP3 yet if it'll cause this same problem on that computer too.

I have no idea if you'll need logs from programs like Hijackthis and the likes but I'll include a HJT log just in case it's needed. Also, my system should be virusfree. I'm using up-to-date firewall (ZoneAlarm) and antivirus program (Avira AntiVir Personal) and checking it with Spybot Search & Destroy every now and then.

I'm also going to include output from 'netstat -a' since I'm not sure if there should be all those ports connected

My router is WRT54-GL and all of my 3 computers are in the same LAN with NAT on, my linux machine is in DMZ.

 

Sorry for double posting, but I wasn't able to find an edit button.

I did some further tests and noticed that I can download one file at only 200 kB/s BUT I can download multiple different files (even from the same server) all at 200 kB/s but a single dl will hardly go faster. So the total I can download is indeed the total of my connection (seemed to be around 800 kB/s at the moment) but for a single file the maximum with this SP3 machine is only 200 kB/s.

On my linux machine I can download even one file really fast from the same server though. (In my case I'm using ftp.funet.fi/dev/ for testing)

Maybe this has to do with my windows machine only making one connection for one file while my linux machine makes multiple? Or something, I don't know but it seems weird.

 

I signed up today just to reply to this post. The problem is SP3. I have been banging my head trying to figure out why only one PC in my network is only getting about 120k download speed. Upload seems normal. Download has really suffered. I was about to call my ISP when I ran tests at speedtest.net from other PC's and noticed the tests were about normal.

I uninstalled SP3, and my speeds IMMEDIATELY went back to normal.

 

Let me state that I have a WRT54G, and this is via a wireless G connection, via a USG adapter. I'm running Thibor 15c on my Linksys.