Ps2 Hdd
 

I was thinking about getting the PS2 HDD so i was wondering. Will the PS2 HHD mess up the modchip or the other way around, the modchip mess up the HDD?

You shouldn't have any problems.

Aslong as you're mod-chip has the ability to turn off. (for example magic 3.1)

You shouldn't have any problems playing FFXI online.