Both my PC's have been updated with SP3 without any problems.
Having read various forums' comments, it seems that you have no need to worry about updating to SP3, PROVIDING YOU HAVE KEPT YOUR PC IN GOOD ORDER..DEFRAGS being quite important.
Having said that, the SP3 is only marginally different to SP2 in my opinion and is not really necessary if you use your PC only for run of the mill usage, like Internet surfing and Emails and Forum visits#
cheers
Eddie Johnson

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Eddie from Rotherham
Skype:eddiefromrotherham
www.yamahakeyboards.info