Yes... I had to do it !
[5] For many strange reasons, I had to convert my main work laptop back to a single boot: Windoze XP. It was once upon a time a triple boot Windoze XP, VISTA and Ubuntu machine. However, having gained nothing from VISTA, I had kept it as a simple dual boot Ubuntu 8.10 and Windoze XP SP3. Anyhow... To remove the dual boot, you will find many articles about this specific procedure, but as you are here, just keep on reading.
In simple words and few lines, here is what you have to do:
PS: my recommendation would be to remove Windoze if you don't have any strong dependencies at the workplace ;)
Links:
[1] http://pulse.veltsos.com/category/it/hardware
[2] http://pulse.veltsos.com/category/it/it-general
[3] http://pulse.veltsos.com/category/it/software/software/os/linux
[4] http://pulse.veltsos.com/category/it/software/software/os/microsoft
[5] http://linux.philosweb.com/drupal5/files/image_2_33.png