The only restriction is "How much memory is available to the system". That code works perfectly well here, and I can assure you that even larger arrays are possible.
Um... considering that that array in the original posting requires 750,000 Terabytes (or 750 Petabytes), and that windows 2000 and XP can only address a maximum of 4GB of memory, this is not going to work 'perfectly well', no matter how much RAM you slap into your system. You may be able to declare it, but certainly won't be able to populate and retrieve data from all of it.
Your own example requires 27^572+5 bytes.
Google calculator maxes out at 27^215, which is 5.53616843 × 10^307 bytes. That's a number over three hundred digits long, and still only an insignificant fraction of the total array size you specified.
"Oops?"