Can I use a US memory stick for my Japanese PSP?

Is my old 2gb memory stick safe to use still on my psp (read the detail please)?

• I recently got 5.00-4m33 put onto my psp and got a 4gb memory stick too (both from Laverton market) about 4-5 days later i turn on my psp and it does not recognize my 4gig memory stick then i pop in my 2gig one works like new. I don't know whether (the 2 gig one) is safe to use and put games/homebrew on im thinking the 4 gig was just a dodgy mem stick from the market. But anyone have an suggestions. Im confused should i use my 2 gig for homebrew/games im stuck.

• Answer:

  You can use any memory stick, i use a 2GB one and it works fine.