I can almost be certain that it's my dual core 2.0 Ghz CPU that is giving me problems. I have 3 GB RAM and a 512 MB GeForce 8800 GT . Anything else I can tell you?
And thanks for the link to Tomlong's page, it does have a lot of info.
That CPU is not very powerful, so do not add too many AI-intensive mods. If you add an overhaul (or...two) do not go crazy with the optional NPC additions. You should be able to run most mods, just not with the best performance. Make choices.
I wouldn't go for the complete QTP3 - not even the redimized version. Especially if your planning to use RAEVWD. Personally, I'm using Bomret's normals and some stuff from QTP3 Redimized (Ayleid etc.). Corepc's http://www.tesnexus.com/downloads/file.php?id=18677 is another option - they are not larger than the vanilla ones.
Also, I'd recommend using BAIN for installing texture replacers (well, other stuff as well) as you easily can test out replacers. If you don't like them or you get to much GPU usage you can easily remove them.
Furthermost, your GPU's VRAM is too limited for the full version, really. Even Redimized is just within its limits, but Redimized is optimized for the purpose of making QTP3 an option for 512MB cards. If you add other visual enhancements to your game, that can easily knock your VRAM requirement into the 700s in places, especially cities. Do not use a VWD mod with that card, OR do not use it with a texture replacing enhancement. CorePC's mod uses the same resolution as vanilla, so you could run that with REAVWD. VWD mods hurt performance on any medium-level gaming system. It is just a trade off users make for the aesthetic enhancement. There is also a Redimized Reduced version of QTP3.
http://sites.google.com/site/oblivionpoinfo/installmods/aestheticoverhaulinstallorder <-- links to the various QTP3 options here, as well as patches
If you want to try BAIN, see the BAIN guide in the Walkthroughs section of my site.