Bugcheck Error Help

I need some help tracing my reboot problems down.  First of all, my configuration:

Dell Dimension 4600
P4 2.4 GHz HTT 800 FSB
1.5 GB DDR PC3200 400 MHz
40 GB OEM 7200RPM Hard Drive Ultra ATA/100
40 GB Seagate Barracuda 7200 RPM Ultra ATA/100
Samsung 48x CD ROM
Lite-On Combo LTC-48161H 48x CD R/RW - DVD ROM
ATI Radeon 9800 Pro - Catalyst 4.1
Dell UltraSharp 1901FP
Windows XP Home SP1
Office 2003

I am getting random reboots.  When I check the minidump file (below) it is giving me information to help track down the error, but this is where I am failing.  Can someone point me to the right direction of what to look for?

I haven't installed any new hardware.  I have tested my memory using memtest and Microsofts memory test and all is fine there.  I have updated all of my drivers since the problem started happening, but this has not helped.  I have scanned my computer for viruses, all good there.  I have also run chkdsk, also good there. 

I have searched google and microsoft for keywords in the bugcheck file, but no go.  The error code 10000050 seems that it could mean any number of things from what I have read.  Can anyone help?  I thank you in advance.

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*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
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Unknown bugcheck code (10000050)
Unknown bugcheck description
Arguments:
Arg1: 80000004
Arg2: 00000000
Arg3: bf87994c
Arg4: 00000000

Debugging Details:
------------------

Could not read faulting driver name

READ_ADDRESS:  80000004

FAULTING_IP:
win32k!vExpandAndCopyText+21e
bf87994c 8b7804           mov     edi,[eax+0x4]

MM_INTERNAL_CODE:  0

DEFAULT_BUCKET_ID:  DRIVER_FAULT

BUGCHECK_STR:  0x50

LAST_CONTROL_TRANSFER:  from bf879bfe to bf87994c

STACK_TEXT: 
a915d198 bf879bfe 00000008 bf953531 a915d794 win32k!vExpandAndCopyText+0x21e
a915d850 bf8775a6 00000000 e30d1000 e303b5c0 win32k!EngTextOut+0x5a9
a915d89c bf87daf6 bf879a2e a915d920 e2cf0600 win32k!OffTextOut+0x6f
a915d930 bf872f3b e2cf0600 a915d98c e303b5c0 win32k!SpTextOut+0x9b
a915dbb8 bf8449e7 a915dc04 e2d3b4dc e2d3b538 win32k!GreExtTextOutWLocked+0xf5c
a915dbfc bf86ba14 e2d3b008 00000018 000000d0 win32k!GreExtTextOutWInternal+0x65
a915dd38 805306a4 17010c43 00000018 000000d0 win32k!NtGdiExtTextOutW+0x222
a915dd38 7ffe0304 17010c43 00000018 000000d0 nt!KiSystemService+0xc9
0012c0a4 00000000 00000000 00000000 00000000 SharedUserData!SystemCallStub+0x4

CHKIMG_EXTENSION: !chkimg -d !win32k
    bf87993c - win32k!vExpandAndCopyText+20f
 [ 48:40 ]
1 error : !win32k (bf87993c)

MODULE_NAME:  memory_corruption

IMAGE_NAME:  memory_corruption

FOLLOWUP_NAME:  memory_corruption

DEBUG_FLR_IMAGE_TIMESTAMP:  0

MEMORY_CORRUPTOR:  ONE_BIT

STACK_COMMAND:  kb