I'm not positive, but I believe (??) that rdesktop requires at least a kernel verison of 2.X or better. If you are using an older version, I'm sure you have your reasons, or perhaps you should consider an upgrade. The 2.x kernel source is available from
http://www.kernel.org
Kernel-HOWTO.
Depending on your linux distribution, you may or may not have XFree86 installed on your system. If you don't, then download the software source from
http://www.xfree86.org/
XFree86-HOWTO.