Such is usually not the stock OS install and what I run into is missing or old motherboard and other drivers. Tell me the version and date of your motherboard driver package.
Also, if you feel like it, look to http://downloadfinder.intel.com/scripts-df-external/filter_results.aspx?strTypes=all&ProductID=816&OSFullName=Windows*+XP+Professional&lang=eng&strOSs=44&submit=Go%21 and I see November 21, 2006.
I am running win XP prof on a Dell 6400.
I had MS Active sync 4.2 and used to sync my PDA phone( O2 XDA ii ) running windows mobile 2003, with outlook 2003 with no issues.I recentlyn updated to active sync 4.5( from the microsoft site).
Recently my broad band had some trouble and hence i began using the inbuilt dial up modem ( conextant) and since then i am not able to Sync the PDA to the PC.
I tried uninstalling the Modem as well as active sync and again renistalling , as well as trying the older versions of active synce like 3.7 , 4.0 with no success.
I guess it is some issue with the COM ports which i am unable to figure out.
I also tried Sync via Bluetooth( toshiba 350 card on Dell) with no success( it was smooth earlier)