Its unclear on how your system32 is missing my guess is you could of deleted it, but you would need to login to ubuntu and look at the xp os driver or partition and look for the file to see if it is actually missing or some grub issue.
You would need to follow some documentation in order to know for sure. https://help.ubuntu.com/community/RecoveringWindows
Usually it is more of a hassle then it is worth in my opinion as I just completely switched to Ubuntu and have a different system if I need Windows. Which for me isn't often. Maybe if I want to watch Netflix at this point(But I have a roku). Most games work with Wine. It takes time to learn all the new programs but the process of rediscovery is fun and you might just learn more stuff then you knew on Windows in the process because Ubuntu/Linux people are pretty excited about the technology.
The easier questions to answer like "how can I find my files?" or "Can I import bookarks from firefox run through xp" or "msn"
You can't see your files from XP because windows doesn't have the drivers to view the linux file systems at least drivers that are decent. You would need to store files you want to share with XP on the actual XP drive or an NTFS partition/drive or an external drive.
You can't import your bookmarks directly, but you can keep them in sync with Firefox sync or even a cloud service like Ubuntu One.
There isn't MSN of course it is a Microsoft product and Microsoft is a competitor of Linux and Ubuntu, but there is an Instant Messaging client. In fact there are TONS. Try Empathy or Pidgin. They work with TONS of different instant messagers not just MSN.
Hope this helps.