Errors in Win XP Pro

[PiX3L]

I have been recently having problems with my computer doing certain things. One of those things is running video files from the internet. If I play the video file in Internet Explorer, it gives me some error message about the data being "read." If I try running it in Windows Media Player, same thing, except Windows Media Player crashes. Another thing I noticed was that when I go to Start -> Run and type in "C:" it gives me the error message, "The folder 'C:\"C:\"' does not exist." But yet, if I type in "C:\" it works fine. I have tried replacing all the Windows Media Player files, the Internet Explorer EXE file, and the Explorer EXE file from the original Windows XP Pro CD with no luck. Any ideas on what might be wrong? Thanks in advance.

-Mike

P.S. I have included my PC stats.

AMD Duron 950 MHz
384 MB RAM
40 GIG HDD
16X DVD-ROM
40X12X40 Lite-ON CDR Drive
GeForce 2 MX 100 32 MB
Windows XP Professional
(I don't know what else you need, but if there's something, E-mail me)