Helo everyone, I have hard drive that I want to use and I want to hook it up to my computer to erase everything from it and install Windows Xp so I can use it on another computer. If anyone can help me I would appreciated it :)

You need to install it into the computer you're going to use it in. XP installs drivers based upon the hardware, so it really needs to be in it's permanent "home" during installation. Yes, you can do it your way, but it would require more experience than you have (I'm not being disrespectful) to transplant it into a different PC.

You want to install XP on this HDD and use it in another computer? Why not put it in the other computer and install XP?

I agree with the above. Installing XP on one PC and then moving it to another is a bad idea. You are asking for problems.

Is to give or sell hard drive with XP pre-installed the only{ good } convenient way.Is that why your not just putting it in the correct computer to start with?

Yes, you should install the OS with the drive in the "other" computer. But your concern about erasing everything is not clear. What you do depends on how sensitive the information is and who is gong to get the computer. See this to review your options. Basically, if it's going to a family member, reformatting before installing the OS should be enough. If it may go to someone who is "nosy", you can use a wiping program, like Norton System Works Wipe Info which will write 1 and 0 at random on all unused disk space after you have installed the OS. Good luck!