Computer freezes when I try to dial up

I've had problems with my win xp computer ever since I
installed SP1 about 4 months ago.

It freezes up for no apparent reason and the only way to
fix it is to hit reset.

Lately it's gotten worse, now it takes 4 or 5 attempts
just to get online. when I open my modem just as the
computer is logging on, it freezes up.

I've run all the xp patches, and I've replaced just about
every piece of hardware in the case trying to find the
cause of this problem.

I'm running xp on an amd 1.4 gig processor with 512 megs
of ram, so I know it's not running out of resources.

I was told that SP1 reflashes your BIOS and i may have to
reflash it myself, but I really don't want to attempt
that if i can avoid it.

If anyone has any Ideas I'd really appreciate the help.

Thanks!