no no no
you could cause severe damage to the PC3200 chip.
although you would have thought that it would be backwards compatible, it's not.
it may run for a while, but then your machine would probably freeze up and you'll have to turn it off from the power point.
i know this as I done it myself.
i thought "ah sod it. it'll be fine"
how wrong i was. my machine froze every 10 minutes.....eventually, as im as stubborn as an Ox - i left the RAM in there and it burnt out.
running different speed RAM is not a good idea. underperformance is as damaging as overperformance.
sell your lower end mem on eBay and just get a strip of PC3200 to match your new one.
you dont want to burn it out completely, then it'd be useless.
good luck