Interesting. That's a rarer one.
These ones are typically caused by an underlying problem on the PC that can also cause Windows Updates to fail to install. So my main strategy with them is to apply the Microsoft documentation on the parallel sorts of problems with Windows Update. If we can get that fixed, that can clean up the iTunes install trouble +en passant.+
In this case, the documentation trail on the 0x8007054F at Microsoft led to documentation on a different error message code, the 0x8000FFFF, which I've also seen associated with iTunes install trouble of this kind. So let's try the *method 2* fix for that from the following document:
[Error when you download updates using Windows Update or Microsoft Update: 8000FFFF|http://support.microsoft.com/default.aspx?scid=kb;en-us;946414]
After applying that, head to Windows Update and attempt to stock up on any updates that you're behind on. (You may need to do this in several batches. Essentially, keep going to Windows Update until it stops offering you new updates.)
After you've stocked up on Windows Updates, can you get an iTunes install to go through, dmac?
