Just get a 2500+ and up the FSB to 200Mhz and you'll have a 3200+ barton core for 80 bucks
Not if his board won't allow him to lock the AGP bus, inwhich it'll then be pointless to buy that CPU being that the only way he could OC is by raising the Multiplier which is pretty much guaranteed to be locked on that CPU.
Don't suggest that CPU unless you can give full details on what they need to OC it and what they should expect.
The XP-M's are the best overclockers with unlocked multipliers, low voltages and low heat, BUT you still gotta be able to lock the AGP bus.
Semprons are low end processors man. They are absolute crap.
They are the next step after durons. They aren't number crunchers and OC'ing would be next to pointless. If you're going to upgrade stick with the Athlon XP series (not to be confused with Athlons which is a completely different, previous gen processor)
Semprons are completely NOT for gaming.
If you can lock your AGP bus then your best bet is to get a 45w 2600+ XP-M , change the FSB from 133 to 200 in the BIOS and then up the multiplier for a higher clock speed if you so wish to do so
I suggest if you even remotely consider OC'ing an option then read the 'Basics to Overclocking' sticky at the top so you know what I'm talking about when I say AGP bus