Slow Broadband on One Machine

I have three computers connected to my broadband network and all usually connect at roughly the same speed. Now, one of my machines (running Windows 7 x64) will only connect at about one tenth of its usual speed. I would be very grateful if someone could 'shine a light' on this problem for me as I am totally stumped (and being a not very techie silver surfer doesn't help when it comes to networking)!

Not sure if this is relevant to your problem - but a while ago I was using a usb wireless device to connect to the router from a Win7 desktop. The usb device/connection started to play up a bit so I installed a PCI wireless card in the Win7 machine and now everything is fine.

There are so many possible causes of this. First thing to verify though - is the machine in question using a wireless connection and when you checked the speed, did you have a microwave on the go somewhere? (Or did your neighbour)

Was it downloading Windows updates at the time?

I ask since this seems to be something that's "just started happening" as opposed to something that has always been a problem.

Thanks to both 4M2 and MarkHampshire for your replies. I will try to answer your queries in order -
The machine in question is connected via Homplug adaptors, I have tried replacing these but get identical results. The slow speed has been going on for a few weeks and is near constant. No microwave on and we live half way up a mountain so nearest neighbours are half a mile away. No downloads going on at the time of testing the speed.
I have been using two speedcheckers (TBB and speedtester.bt.com) and both give the same results.
The only thing that I can think of that may be connected is updating the Realtek PCIe controller driver. I tried reinstalling the old driver but there was no change.

Are one or both of the other machines also connected via Homplug adaptors? What operating system(s) are you using on the other machines? Are you using public and/or shared folders for networked file sharing between the machines?

Hi -

One of the other machines is running XP and is wireless, the other is Windows 7 x32 and is cable connected. Re the folders, I am not sure about the public/ shared. I don't actually do any file sharing as such, just the broadband connection.

Starting to look like a Homplug connection issue, perhaps? Same antivirus software and firewall settings on both Win7 machines?

I had already tried swapping out the Homeplug adaptors but got the same results so tried swapping out the ethernet cable... no change. Have now tried plugging into a different wall socket and guess what?... problem solved.

Thanks guys, I am now away to puzzle out what can change on a wall socket.

Homeplugs are best plug directly onto the ring main.

They can go slow plugged into spurs or extension leads.

It might be worth checking the particular socket with some safety test equipment