XP SP2 Install Error: Atapi.sys is in Use by Another Program or Application
Contributed by David Kirk 
Tagged: Windows Several programs can cause this inability to backup atapi.sys when trying to install SP2. Here’s the deal.
Multiple people are reporting that they are getting “atapi.sys” errors during the installation of xp sp2.
This error is caused by programs that create virtual hard drives on your system such as Daemon Tools and Alcohol.
If you see this error, cancel the installation and disable these programs. For me, turning off alcohol was enough. Other users have reported that they had to completely uninstall these types of programs before installing sp2.
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IT said on December 23, 2008
Unlocker.exe, google it. Unlock windows-system32-drivers-atapi.sys and click “retry”.
Name said on October 8, 2009
thanks a million mate
danhur said on October 28, 2009
OMG Thank you, wish i had known about this already. wow