Playback problems after Winows XP reinstall

Yesterday I reinstalled Windows XP with SP3 on my Sony laptop and installed Musescore 1.2. Now playback of .mscz files from my backup on a memory stick is distorted and sluggish. The blue playback line breaks up and does not seem to be able to keep up with the notation and where the play backsound has reached. As the score becomes more complex, i.e. more than one stave, playback speed decreases and distortion increases. Something seems out of sync. Uninstalling Musescore 1.2 and reinstalling 1.0 or 1.1 does not solve the problem. Otherwise the .mscz files seem to load from the memory stick without any problem.

Previously, prior to reinstallation, Musescore 1.1 and its .mscz files ran very happily on this laptop with Windows XP and SP 3 without any such problems.

The same .mscz files, on the same memory stick, run perfectly on my desktop machine which runs Musescore in Ubuntu Version with MuseScore 1.0 and Windows XP with SP3 with Musescore Version 1.2 (dual boot).

I cannot detect any other problems with the laptop reinstall of Windows XP SP 3, but the logic of the problem seems to suggest this might be the source of the playback difficulties.

An help would be much appreciated.
Bill
PS Note entry now seems much slower. The note being entered sounds as soon as I hit the keyboard, but the note seems to take much longer to appear on the score, about a second. Playback is still distorted as above when I playback a newly notated piece. I think another reinstall of Windows XP might be called for - sigh!!