So I'm starting a fresh install of Oblivion running basic FCOM (OOO + MMM + Frans only) and some rather large quest mods (Lost Spires, Reclaiming Sancre Tor, Werewolf - Legends of the Norths, Ivellon, Adense Epic Dungeon, Verona House Bloodlines SI Fixed, Ayleid Steps, etc), with minimal graphical enhancements. With mods that have a lot of loose mesh, texture, sound, etc. files, I've been making BSAs to tidy things up and hopefully increase performance.

So far, there are about 3,000 files in my mesh folder, and another 3,000 in my texture folder.
To the veterans of Modblivion, are those reasonable amount of files in my mesh and texture folders?

PC Specs:
C2D E6750 (OC to 3.2Ghz)
WinXP 32-bit SP3
RAM: 4 GB
MSI NX8800 GT 512-mb (factory overclocked)
500GB HDD (only around 10 GB free space after complete install).
1920x1080 monitor (22 inch or so)

If your game runs fine, and the files belong to mods you have currently installed, then yes! That is a perfectly reasonable number of files.

That's not a problem --- Mine currently has 35,511 texture files and 21,361 mesh files and runs fine

Yeah, so far so good. I've been spending the last several days trying to get a stable set-up going, and from reading about how a clutter Data folder can decrease performance, just a bit scare of the number of files. Much ado about very little I guess

Honestly, you are more likely to run into problems with excess BSAs than with a few tens of thousand loose files.

Excess meaning the game won't load more than 400 total .esm, .esp, and .bsa files combined. Up until that point, you will see a slight performance gain having uncompressed bsa files instead of loose files, but it is slight. I myself .bsa everything except replacers just for ease of use.

I would suggest you to change your OS...install the 64 bit version of win7. I noticed a lot of improvements with all games. Stutter when oblivion loads new textures is now almost disappeared.