Problem with wireless connection

Apologies, I'm sure this will be a simple fix ... my excuses being I'm not great with computers, I've been off work ill and got about three hours sleep last night!

We have three laptops:
A - runs XP, has no wireless adaptor, is directly connected to the modem/router (thomson 585 v7), can connect fine to the NAS drive which is hooked to the router, can connect to the internet - everything fine. This I use for downloads and generally messing about
B - runs Vista, can connect fine wirelessly to the NAS drive and internet - also fine. This we use as a machine for my wife and kids general internet use.
C - runs XP, has a wireless adaptor, and is used occasionally by me as a wireless machine - this is the problem child.

It was connecting fine to the internet, but ever since I changed the modem/router, it lost the ability to connect to the NAS drive without the NAS drive asking for a security password. I really can't remember what happened at that changeover point.
I had put up with this, but in my confused state today, I decided to try to fix this.
I typed in what I had written down as password but no joy.
In 'My Network Places', the modem was appearing twice (it's the same on the other XP PC) so I decided to rename one.
Both disappeared.
I lost connection to the internet.
I checked my wireless adaptor, which is still saying I have an 'excellent' connection.
I attached it directly to the modem/router using the ethernet adaptor, still a problem.
I then disabled my security suite
Tried again and could then connect to the internet - this may be co-incidental, but I'm not really thinking straight at present.
I started to think about enabling a new firewall/scanner etc and then thought WHOA!, lets sort the basics out first.

Can someone please direct me to what I must change to at least get wireless internet working again ... I'm sure I'm going to break something else if I just mess without expert advice!

Thanks.

 

Update:
Rebooted laptop and can connect to the internet using ethernet with security software enabled, so that was a red herring.
So I then guessed that the computer is seeing the wireless signal from the router but not pulling a valid IP address?
The wireless adaptor confirms this - the IP Address is blank
So, somehow I need to re-create my network connection?

By the way, I should have said that I would have tried to re-use the CD that came with my router, but have no idea where it is - we had to pack a lot of stuff away when we had some work done on the house and a lot is still in boxes in the spare room.

 

Ok, I knew I wouldn't be able to stop messing.
Decided to use system restore, and took it back to yesterday's checkpoint.
I got the somewhat reassuring (!) message that a 'device with a duplicate name exists on the network' while it was logging me on (this was the problem I was first trying to fix).
My wireless adaptor now has an IP address and I can connect to internet.

I still can't access my NAS drive, but that's for another day, I'm off to bed.
If anyone has any thoughts on that, all gratefully accepted.

Thanks and goodnight.

 

What brand and model number is your wireless adapter? Have you updated the firmware on that adapter lately?

 

Right, I decided to remove Zonealarm security suite from this laptop, and install a cocktail of PC Tools Firewall, Avira AntiVir, Comodo BO Clean and Threatfire.

Install went ok, but now the aforementioned problem is back ... the wireless card isn't getting an IP address from the router ... no internet

I guess I could roll back as before, but I'd like to know what's causing this so I can fix it and move on.

Any ideas please?

Thanks.

 

... and in answer to the previous question, it's a Thomson Speedtouch 110g.

The only driver I've found on the net is the same as the one installed ... not that the downloads (CNET, Tech Republic)work anyway.

I would try to uninstall and reinstall (?) but I can't find the original setup disc.

 

Decided to rummage round in the loft and found the original box with install disk.

Five minutes later ... uninstalled, reinstalled, all working now.

Bloody computers.

 

Glad to see that it's working. Reading manuals suck arse but they come in handy a times.