Can my system which is P3, 450 MHz with 384 MB of RAM support a DVD writer/combo drive?
yes. but you will have to restrain yourself to smaller writing speeds (if it hasn't buffer underrun protection). that should be a + though, as such speeds are said to make more readable discs.
and it will be recommendable not to surf the net or watch divx movies while writing discs. 
PS: you have not told us anything about the hard disk. it is an important parameter for the capacity of recording optical media! because the system MUST create an image of the recorded disc (may it be CD or DVD) which has the same size with this one. so you'll have to have at least 800 MB free for CDs or 6 (9 for DL) GB for DVDs. you can upgrade (if your PC has not such a big (!) hard disk by means of an external USB2 drive, connected to a supplementary PCI USB2 adapter. (cost approx. 200 $ the whole thing).
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