Hmm..not much to go on there Sami...I assume by P900 your refering to the processor in your PC? In which case it doesn't matter.
Does your machine have a memory stick slot (reader)? You can get an adapter for Mem Stick Pro Duo (the smaller card) to Mem Stick Pro (the larger card).The largest capacity appears to be 1Gb (for the Duo) & 4Gb (for the Pro). You need to make absolutley sure what type reader slot you've got (on the PC), make & model of PC..??
Had a quick look for places to buy, have a shuffty