There is an MS hotfix available for windows 7 to stop Media Player corrupting MP3 files. Find more info here and download from MS here

**Update**

Make sure that when downloading the hotfix that you get the download appropriate for your system. i.e. download the 32-Bit version for Windows7 32-bit and the 64-Bit version for Windows7 64-Bit…

http://buzzinh.geekfreak.co.uk/2009/01/11/windows7-beta-build-7000-on-samsung-nc10/

Going to try this and see if it works.. Will post up again when / later with info more info after test.