The BIOS for Vista is dated 07-2008, Ver. 5.25, file size: 1.58 MB. for the HP SR5325ES Desktop PC. It's exactly the same for the Pavilion a6552f Desktop PC.
I'd be really cautious about trying to load a bios from another series unless the motherboards are identical hardware wise. Doing so can render the board useless if the wrong bios is installed. I'd also be cautious about trying it until you know someone else that has done it successfully. That's the number 1 problem with HP pc's that were shipped with Vista installed and folks not liking the awful Vista OS who really prefer Windows XP over the newer OS.
You can check the HP forums to see if that problem has been encountered/solved:
Code:
http://forums12.itrc.hp.com/service/james/home.do
or a more detailed search can be found here:
Code:
http://www11.itrc.hp.com/service/james/home.do?admit=109447626+1219201614482+28353475
If not, then try posting a request of your own in the forum and perhaps one of the HP experts can help you.
And you might want to keep watch on this thread to see if anyone answers:
Code:
http://forums12.itrc.hp.com/service/forums/bizsupport/questionanswer.do?admit=109447627+1219201165887+28353475&threadId=1247372
And you might want to scroll thru this lengthy multi-page forum of links:
Code:
http://forums12.itrc.hp.com/service/forums/categoryhome.do?hpweb_printable=true&admit=109447627+1219201229609+28353475&categoryId=279&pageNum=5
The moderators on the HP forum should be better equipped to handle your request than we can since they only deal with HP/Compaq pc's.