Personally i don't think your going to see much speed increase whatever processor you put in.
And there's no way way that mobo will take a 2.4ghz pentium your mobo has support for slot A for AMD® -K7 Athlon 200MHz FSB processors
90*/95*/100/105*/110*/115* MHz FSB
AUTO detect CPU voltage, so i don't know where tuneup utilities got that from.
If I were you and others may disagree but a mobo bundle with a 2400 sempron for around £100 will speed things up no end.