Inspiron 8100 problems

I've had an 8100 for about 2 years now with not a single problem.  The only change I've made (about 1 year ago) has been to updgrade my RAM to 320 Mb from the 128 Mb it came with.  About a week ago, it has begun running alot slower.  Everything takes about 5 times longer than it used to (applications, etc.) and it gets even worse when I try to run multiple applications at a time.  Also, the 2 fans at the rear of the unit run constantly at high speed.  Before I would hear them kick on maybe once a day for a brief period.  I have not added any new software recently or made any other hardware changes.  What stands out to me is that this all started the day after I had accidentally left the unit in my car overnight.  The temperature that night was in the single digits (0-5 F range).  I would pinpoint this as the issue except the user manual specifies down to -40 F as acceptable storage temperature but who knows.  I am also wondering if the slower speed and the fans being on are separate issues or if one is causing the other somehow.

So far I have run all of the Dell diagnostics on the CD.  Everything passed for the most part when I ran a complete test all the way through.  I went back and checked the memory separately and it still passed.  However, when I ran the fan tests by themselves (both processor and motherboard), the computer would shut down after starting the test (the fans already being on).  Also, when I ran the complete test I did have 6 failures.  The CDRW write test failed I assume because there was not a writable disc in the drive.  I had 3 failures of tests on the modem (NIC Register test, EEProm test, Interrupt test), I assume because the modem is not connected to a phone line.  There were also 2 other failures I do not know about:  NIC Internal Loopback Test and NIC Bus Master Test.

I have also cleaned up my computer a bit.  I cleared out all my temporary internet files, uninstalled programs I didn't need, ran some software to eliminate spyware/adware files.  I also have had Norton running on my computer for over a year now and run complete scans once a week.

It would seem to me because of the timing that it has something to do with me leaving it in the cold overnight but if anybody has any ideas and/or ways to correct the problems, I would greatly appreciate the help.

Thanks,

Mike