Choosing external Hard disk for laptop

I have a HP Pavilion dv2840se (probably upgraded from dv2000 model by manufacturer). Hard disk is 250 GB, rpm: 5400. No eSATA port as written (I have no experience with eSATA yet; I don`t have a good hold on computer knowledge ).
http://www.officedepot.com/a/produ [...] :142u1tmri

Can I use eSATA in my Laptop?
There is an expansion port 3 in this HP laptop. Does it have any relation with eSATA port? Or what`s its exact use?

Now I am looking for a good external hard disk for storage.
Is is justified for me to buy a 7200 rpm external drive? (As my Laptop hard disk is 5400 rpm).
I usually do not transfer a great amount of data between workplace & home. It will be mostly for storage (& probably back up). Still portable ones looks good, no external power, less weight & size. I am now living in Tokyo. Will be here for 3 more yrs & then have to move. So less weight & no-external power supply sounds nice to me. At the same time I am fancied with the eSATA & 7200 rpm of the bigger ones (1 TB). But they are heavier & when I move I have to think about the power adapter for international use.

In Tokyo (Akihabara) I have commonly seen the Buffalo, WD, Lacie, Lacie rugged among the portables. Buffalo has pretty nice external appearance. Lacie rugged too. Lacie rugged XL....but that is still heavier (>2.3 Ibs) & external power. Can anyone suggest? Which one can I rely for storage over longer years? I have read some reviews where seagate was not suggested.

I am absolutely novice in dealing with PC stuff. I usually just use.
Any suggestion will be greatly appreciated.
Thanks in advance.

Thanks. I was waiting for suggestion.

What do you think about the durability? I mean, how many years can I count on WD passport ? (I will probably use for weekly/monthly update of storage,specially photos or Family VDOs. My job is not much related with IT things & large VDOs).

Is Lacie that much long-lasting as they claim? Or that does not match for Lacie's high price?