NO it wont, 750Mhz AMD has different pin structure and 300Mhz has diferent.
as AMD timeline was as follows, this i'm writing for knowledge base as well)
1: 75Mhz - 300Mhz were on Socket 5 - 320pins --> this is yours
2: 233 - 500Mhz = Socket 7 = 321 pins
3: 500 - 1000MHz - Slot A
4: 600Mhz to AthlonXP 3200+ = Socet A = 462 pins
now you are missing just 142 holes in Processor holder on motherboard.
i'll suggest, get hold of a needle (common pin will as well work) and adjust it in front of drill machine, and drill these 142 holes to accomodate that 750Mhz Socket A (462) pins Processor.
* and bear in mind, a PIN more or a PIN less than specified, your CPU might fail to work. - HAHAHAHAHAHA
+++ all above is joke for drilling , dont take it seriously ++
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