Way way back in the olden days when hard drives over 32MB in size couldn't be addressed, I partitioned my giant 250MB one into eight. I set C as the operating system, D as interesting stuff, E as pictures, F as WP docs, G as spreadsheets, and so on.
That has over the years been so much easier than searching for stuff in one giant "My Documents" folder on Drive C somewhere. The individual partitions are now a tad larger than 32MB, and vary in size from 10GB to 200GB. I've got used to stuff being that way, and I like it. I know where everything is - like "Excel anything is in G:\" rather than "C:\Applications and something or other\My name\My Documents\The budgies name\Excel\..." Thunderbird e-mail is in I:\Mail, not buried about seven layers down in folders with gibberish names.
It means I can back up my stuff selectively - I have a few batch files that do that in one hit - for example:
xcopy G:\Excel\*.* S:\BU%date:~6,4%%date:~3,2%%date:~0,2%\G\Excel\*.* /C /D /S /Y
and job done, with stuff in a dated folder.
It proved a big "plus" when I installed Windows 7 on a spare partition: I can access the same documents folders with Win 7 or XP.
If I were starting from scratch, I think I would do it again. The drawback is that if you size the partition wrong, it's a faff to change it (Partition Magic used to do that for me, but I've not needed it for ten years or more). The advantage is that a hard disk crash some years ago didn't lose any data (it's all backed up anyway, but I didn't need the backup).