T43 won't boot from CD/DVD (or USB)

[runbei]

Absolutely unable to find a solution for this; I've searched high and low but can't find an answer to this problem:

My T43 has a DVD/CD-RW drive and won't boot from that drive; neither DVD nor CD nor USB stick, no matter how I set the boot order (I'm trying to boot a linux install DVD.). I see lots and lots of posts from people with the same problem in this and other models, but no solution at all. Is it a fatal, un-fixable flaw?

Moderator edit: Merged contents of two almost-identical posts, deleted one of the (almost identical) posts.

[RealBlackStuff]

Most likely it's the Southbridge chip going South (big Intel chip under wifi-card).
Plenty of posts here about this problem.

[runbei]

I'm inclined to think you're right. Wondering if it would account for the other big and seemingly worsening problem with the laptop - WinXP working normally for a while about one boot out of three, other times slowing quickly to near-freeze. I'm sensing it's time to replace. Thanks much for the advice - very helpful.