Had this Dlink Air plus router with an wireless adator set up on with a PC running win Vista, but as the PC had problems I tried it with older XP PC and it worked fine for about 5 weeks but tonight the wireless adaptor on my desk has stopped flashing and I could not access the internet so I decided to try the Vista PC and it works fine on there, while it can get me online I would still like to fix the D Link to work with the older PC again if anyone has any idea as to what is the problem as it is a faster more reliable PC
Is the dongle the DWl-G122 which was very popular back in the days of XP? If so, and I still use one for XP machines, your problem is related to using the correct driver. If the XP machine has just had XP Service Pack 3 installed that would explain why it stopped working - D-Link released a new driver to cope with it.
In any event, you need to check on the back to see which hardware "revision" your adapter is. (I suspect it will be C) Follow this link D-Link DWL G122 Drivers and enter the revision to download the correct driver. For revision C there are 3 available. The most likely driver release you need is not the newest but V3.40 but download them all just in case.
Firstly uninstall the current driver and reboot. (Do this every time before trying each driver) Install the new driver and plug in the adapter only when told to do so. I have found that once installed the adapter may not work until another reboot. Always use the Windows Zero Configuration and not the D-Link utility option at the end of the installation routine.
These were very reliable wireless dongles and I must have installed dozens over the years. I have only ever had one that failed completely after several years. As I said I still use one when repairing towers with no wireless connection built in.