When did preshot come to S478? Preshot came out with the S775 chips, never knew they were on S478. Also doesn't seem to make sense to make a preshot without HT.
"Worth it" how? Or when you do what? Both chips are old and dog slow compared to whats out today. $9 isn't much so if you do a lot of CPU intensive tasks it might be worth it. (more programs use multicores today then they did back then so a HT CPU should perform better then they used to.) But what you really need is a new system. Even a $299 dell would be faster then what you have.
Socket 478 eh? That's a dead end. If you had 945/965 series motherboards (LGA 775), you might have had a chance with the Core 2 Duos.
Its best for you to start saving for a new PC. For 400-500$ you can get a much better PC today than what you currently have.
please please upgrade to atleast an athlon x2, the difference will be incredible, if you can spring for a athlon x4, you will need a new mobo and ram for these cpus but it is so worth it, noone should feel the pain of a pentium 4 anymore