Vista works, XP doesn't?

[ohhmyylantaa]

Well, I have two computers in my house. Mine runs Windows XP and the other runs Vista. Strangely, since I've heard Vista likes to crash this game, I can only play on the Vista. When I play on my XP I crash every time I sail. Fun..., right?

The XP (a two year old eMachines):

• 2.93 GHz processor
• NVIDIA GeForce FX 5500 graphics card
• and a normal Intel graphics card that came with it that I don't have active
• 512 MB of memory
• a buttload of free space on the hard drive
• hardwired high-speed conection

The Vista (a two month old Dell):

• some normal Intel graphics card it came with
• the same hardwided high-speed connection
• 1.60 GHz processor
• 1013 MB of ram
• tons of free space on the hard drive as well

Like I said, the Vista works wonderfully (well, except for lag ). The XP will always crash at sea. Sometimes I takes several tries of me trying to open Pirates before the login screen will actually show up as well. (Although I think I may have had that problem on the Vista when I first started playing on that as well.)
Now the curious thing is that the Vista used to do the same crash, but it stopped after several annoying tries and will now never do it.

Does anyone have any idea what could be causing this? Any help? Because it's quite annoying to have to steal time on the other computer when mine sits neglected with its nice new flatscreen.