What does this mean when trying to install sp2?

The file c:\windows\system32\drivers\arapi.sys is open or in use by another application... I get this message when I try and install sp2 please help.

my rig.
asus A8V deluxe bios ver 1005.020
athlon fx 53
x800pro
2x 200gb baracuda sata h/d
win xp pro.

p.s have used sp2 on my old system without problems.

I think you mean atapi.sys.
Try this,,,,,,,,,
http://www.annoyances.org/exec/forum/winxp/1088544272

You could also perform a "clean boot" and then install SP1a or the SP2 beta.

How to Perform a Clean Boot in Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;310353&Product=winxp

Visit: http://www.microsoft.com/windowsxp/downloads/updates/sp1/default.mspx
and select "Network Installation", download SP1a to a new folder, then install...the same applies to the SP2 beta.

or try installing Sp2 when in safe mode, to get into safe mode boot up, and before you see the windows logo keep pressing F8 untill it gives you the option to boot into safe mode.