A week or so ago, I suppose, my internet connection has suddenly slowed down. At first I thought it might be because I had downloaded TCPOptimiser which makes changes to the registry, but I imported a backup registry and the problem persists. The family computer has also suddenly slowed down.

And when I say slow, I mean nigh on unusable. It will vary, so that sometimes it almost seems fine, but I generally have to disable and then re-enable the wireless connection on my computer several times a session (it seems to work best after this). Even google takes a couple of minutes to load, and I find myself being constantly signed out and reconnected to google talk, although the wireless connection shows no interruption.

However, the third computer in my home seems not to have suffered, and the only link I can find is that the two slower computers use PCI wireless cards, while the still-working-fine computer uses a USB wireless.

Anyone know anything that might have caused this?

Have you got decent encryption on your wireless connection (ie WPA)? It does sound a bit like someone is freeloading, although the third computer working fine is a little bit of a mystery.

Have you done spyware checks?

Also, when it's slow, bring up the task manager and go to the processes screen. Click on the CPU column twice to sort by highest CPU user, and look for any strange processes that are consuming a lot of CPU.

If the TCPOptimizer is the problem, you may have to uninstall it. While I'm not familiar with it, it doesn't appear to be a malware tool. Have you verified that the settings that you've changed with it are correct?

The wireless is secured with WPA-PSK...

And no, no spyware on my computer... That I can find at least... And I'm pretty sure I would have found it if it was there...

TCPOptimiser doesn't seem to be malware, and I don't think it runs at all... It just seems to change settings, and only that...

PCI Cards are better than USB sticks for wireless - so that's not the problem.

You're secured by WPA - PSK, so that's not the problem.

Have you recently bought anything electronic - a microwave or the like? Try changing the channel you use your wireless on, there might be something conflicting with the wifi setup.

Haha... Got a new iron... Haven't checked the manual... might be one of those new transmitting ones ;)

How would I go about changing the channel?

Although having said that... it appears to be better at the moment...