Hi,
1. Was it working before?
2. Have you made any changes to the computer prior to this issue?
I would suggest you to follow the mention Microsoft article and check if it helps.
How to troubleshoot Bluetooth detection and connectivity problems in Windows XP Service Pack 2 : http://support.microsoft.com/kb/883258
Also refer : http://support.microsoft.com/kb/883259
Note: Important this section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: http://support.microsoft.com/kb/322756