Installing DirectX9

I have currently been trying to install DirectX 9.a and i
keep getting this error message saying that i have a
windows that is not compatible, but i have Windows XP
Professional and that is supposed to be compatible. Is
there anyway around this or something else i may have to
download in order to install DirectX9.a?

>Yah, I have a question related. I finished installing
DirectX 9.a assuming it was compatible and not really
caring for the message it gave me saying it wasn't
compatible. I can make the connection now that my computer
wont start. It boots and everything but when loading
Windows XP it tells me that there is a problem with
lsass.exe and that it doesn't accept my password. WHAT
PASSWORD?! Will I have to use my Recover Disk?