How did you format it originally? It might have shipped with FAT32 for "universal compatibility" (but, as you have found, limited usefulness). In the Windows world you have to go with NTFS, or else it will not accept any single file that is larger than 2GB.
You could use a utility program like QuickPAR to chop a big file up into pieces of 2GB or less.
(Haven't gotten into it heavily, but it's kind of cool for stuff that you really want to survive; it chops a file into pieces and then makes redundant
parity blocks, so even if multiple pieces are damaged, you can still recover by feeding the reconstruction program with parity block files until it has 'enough' redundancy to recreate the missing bits. It's like RAID 5, only for a single file. The binary newsgroups use it to send entire DVDs around, knowing that it's almost impossible that ALL the parts will make it unscathed. With enough PAR files, they don't have to.)
If you've got stuff on it, then running the defrag "analyze" step will give you a quick visual showing how badly your data has been shotgunned all over the platters.

If you're just getting started with it, I'd reformat the sucker into NTFS.
Lacie makes pretty good stuff; AcomData is almost a clone and mine have held up so far (knock wood!). Nice heavy aluminum heat-sink cases.