Are they being played from the one drive (your hard drive)? Anyway, start doing clean up. Run Disk Cleanup, uninstall any of the programs (and CODECs) that you don't need. Check you have plenty of space (on your Windows drive). Do a defragmentation.
You can try uninstalling and reinstalling (an updated version of) the audio manager software and drivers.
Run Error Checking (CHKDSK) on your drive/s, especially your Windows drive. Have you tried running the files from a different drive (say, copy them to an external USB drive)?
Check for an update for the chipset drivers at Acer. It looks like it's an nVidia 630i chipset, but it may be manufactured specifically for Acer, so I would get my updates from Acer, not nVidia.
Please put details of the Windows version (Vista) and Service Pack level in your User Profile "My System".
[PS Please try to separate your thoughts into discrete sections and use punctuation, like capitals. It makes it so much easier to read