Well in that case create an account in Thunderbird and import these stored e-mails into that account.
It's exactly the same way that you would do it in Outlook.
I don't think that you'll find that there is anything wrong with your computer other than the fact that it may lack a bit of processing power and falls over in manipulating these large files so you get the error message pop up but even if you could open one pst file it would be mostly junk in HTML code.
Remember that outlook doesn't store individual E-Mails separately but stores the entire contents of a single folder as one big file that may contain thousands of individual e-mails.
But if you are worried about your computer then download The Ultimate Boot CD and run some diagnostics to see if everything is working correctly. It's available at
http://www.ultimatebootcd.com/download.html
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