ok, so you want to install xp on the compaq machine.
first of all you must ask yourself if you really want to install xp? windows 7 is so much better in so many ways, and xp can be a pain to install on some machines.
if you do really want to go ahead and install xp, then the best thing to do first is to make sure you have all the drivers ready. a driver is something that windows needs to make sure all your hardware works correctly. sometimes the XP install disc has the right drivers on it, but not always, so it's a good idea to make sure you have everything in case you do need it.
you can find the drivers
here.
you'll need to download the audio, chipset, graphics, touchpad, network and storage drivers.
i'm not sure which of the wireless network drivers you'll need - it seems that compaq/hp sell slightly different versions of your laptop. to see which drivers you will need, you will have to look at device manager under windows 7 to see what network hardware you have - then download the relevant drivers - for instance if windows 7 tells you that you have intel wireless, then download that one for xp.
once you have downloaded the driver, do not try to install them in windows 7 - you will need to put them on an external drive or burn them onto a disc - you will need these after installing xp - install each driver in turn, you'll probably have to reboot after each one - it will take a long time.
ok - now let's talk about how to boot from the xp install disc. maybe your laptop is already set to boot from a cd - if so, simply insert the disc and boot the computer - the xp install process should start automatically (but slowly).
if your machine doesn't boot the disc on its own, you have to tell it to. when you start your computer up, you should see a message similar to 'press F2 (or delete or some other key) to enter setup' or you may see something like 'press F12 to change boot order' - i don't know what your machine has.
please report back what message you see on the screen when you start it up, and we'll take it from there.
my advice is so stick with windows 7 - you will save yourself
a lot of trouble. why exactly do you want to install xp on it?