There are two paths you can take but I've just tested one: 1)Use Wine in Fedora to run mstsc.exe in linux and simulate .exe runtime environment.mstsc.exe is in your windows\system32 directory or can be easily downloaded from microsoft.com website. 2)Use VNC.It means that you should download WinVNC on windows XP which would act as your server.And use VNC client that you use in Fedora to access your Windows XP machine.
The second solution that I've also tested is much better because it doesn't throw the currently logged in user out but the first one does because of windows XP limitation of one user at a time.
I see that using VNC method will leave the windows system open i.e. others will be able to see what i am doing on that PC where as, while using mstsc, it will just showing that the PC is locked. Is there any way to achieve the same effect through VNC?