System crashes all time after update installations!

Hello all,

After recently installing the some windows/etc updates
from the microsoft site the computer has started to
really go off the rails and crash all the time. Namely,
when a dialog box pops up e.g. the 'send mail now' one,
any kind of error, even when MSN messenger comes up
with 'now online' pop-up. When this happens, it freezes,
ctrl-Alt-Del doesn't work and the only thing I can do is
turn the power off.

Could anyone help me at all please, as I 've tried taking
off these updates, but nothing has worked! The updates
I've just installed are:

Security Update (KB823182)
Security Update XP (KB825119)
Security Update XP (KB828035)
Windows Media 9 Series Codec Package
Recommended Update for Windows XP SP1 (KB822603)
Security Update (KB824141)
Security Update (KB824105)
Update Rollup 1 for XP (KB826939)
S3 Graphics, Inc. display software update
C-Media multimedia software update
Recommended Update (Q322011)

The only other thing I can think of is that all of a
sudden the 256mb RAM isn't enough, but that's a long
shot. Especially since it was never a problem before.

Any help would be greatly appreciated, as I don't wanna
have to format the drive! Please feel free to email.
Thanks
Leo Edwards