You cant swap HDD's.If you HDD swap it will format your harddrive and you would lose everything.
Do you still need help with data transfer?
Its pretty easy all you do is
go on your 3.55>settings>

ata transfer>then select transfer from this ps3 to another.
then go to your 3.61>settings>data transfer>then select transfer from other ps3 to this system.so the 3.61 would be recieving.
It does not delete anything off the 3.55,but it DOES delete everything on your 3.61.
Hope i helped and im sorry if i missed anything.:\
---------- Post added at 12:57 PM ---------- Previous post was at 12:55 PM ----------
Originally posted by Truce
Alright! So I got my chick to give me her PS3 earlier, because I wanna go online and **** around with my MW2 patch. Here's the problem. The data transfer shit...is confusing. I'm not 100% sure how it works, and before I do...do it...then I wanna know it works. I've got her PS3 updating to the latest firmware right now, which is obviously 3.61, and when that's through, I'll data transfer from MY PS3 first, to hers. Then it's telling me I have to transfer from her system, back to mine once it's done. Is this right? I'm new to this data transfer shit, and I was wanting more information about it, preferbably for the guys who do this A LOT. All help is appreciated.
Reminded that HER PS3 is on 3.61, and mine is on 3.55 CFW.
Forgot to quote.