8204 software conflicts?/problems - help anyone?

Hi! Just to let you know that I don't have much technical experience and hope that one of you gurus can help me sort my problems out with my 8204.
The problem started with MSN Live when I was using it. It started to lag badly and the keys I was typing seems to be real slooow in showing up on the screen. Then another time, it would do the same and start to freeze. Even the time showing on the taskbar was frozen for about 10 minutes. So I gave up waiting and restarted the machine again.
The next problem is with Media Player V.11. One time it can play the movies I have in my Drive D without any problems and other times it will play the movie and for no reason, it would come up with error messages like
- "Haali Media Splitter: AVI: Stream count does not match stri contents"
- "Windows Media Player:ncannot play the file. This can occur when another program or operating system component encounters a problem but does not communicate the nature of the problem to the player" (when there is no other programs running while the movie was on)
- other error messages telling me that there's insufficient memory (which is a joke as I have more than enough in here) or the processor is unable to process (again that's a joke since as it's a Duo Core) or ePowerManagement DMC.exe...etc
It seems to have a mind of its own, showing all kinds of error messages when it feels like it and I can play the same movie and can have no problems at all. Then if I was play the same movie again, it can show me an error message. I've deleted the Media PLayer V.11 and reinstalled it again but has not solved this problem.
Next problem is once the startup page shows up like it has finished doing the startup then the screen would go black after a few seconds then back to doing the startup again.
Lastly, when I did the defrag. for the first time, it was doing OK then it got stuck at 1% and froze. I got fed up in waiting so I cancelled it.
Now, I have rebooted this machine with the CDs/DVDs that one has to make when one got the machine and it didn't solve the problems at all. So, does anyone have any ideas at all for me? I don't know if Acer service is willing to deal with these kind of problems since as the warranty I believe is only for hardware and not software.
Any help will be most appreciated!!! Should I try rebooting the machine again? I read somewhere about Acer hidden partition and I hope that that has not been lost.
Thanks!