It is a good computer. But, to be honest, Oblivion runs better on my old Pentium 4.
It's pretty average, at best, as a modern gaming PC, to be completely honest with you. And there is
no way a Pentium 4 of any kind will be better. Full stop. Different CPU architecture - it makes all the difference.
Yes, I already know that the game doesn't use multi-core technology and that having four processors working at 2,50 Ghz is worst than having one processor working at 3 Ghz.
No. Again, CPU architecture is the thing here. "GHz ain't GHz", a lot of the time. They don't translate between, say, a Pentium 4 and a C2Q (like yours).
Utterly different, from the ground up. In fact, the Core 2 series has a more direct link to the Pentium
3. But that's neither here nor there. History, and in this case, it doesn't matter, and besides, could be very misleading.
Oblivion can use 2 cores... kinda. So, your CPU isn't
all wasted. Just half of it or so.
1) Should I overclock my PC just before playing Oblivion, or do you think that this procedure is dangerous and that it's a shame doing it on a young PC?
2) Should I try to install Stream line?
3) The installation of Stream line requires the installation of OBSE (Oblivion script extender). But, for installing OBSE, I should know if I have a Steam version of the game or a Retail version: what's the way to understand it?
1. Overclock only if you are very sure what you're doing. If you feel at all lacking confidence, I recommend *not* doing so. And that seems to be the case, so...
2. Streamline can help a bit, depending. Make sure to use its INI file properly, if you do install it.
3. Where did you buy the game - online/offline? Steam or hardcopy? That's all there is to it.
1) Two days ago I installed Oblivion stutter remover, but it doesn't give me any improvements.
2) I also changed some values in the .ini file (in Documents\My Games\Oblivion), according to an official guide: nothing happened.
3) The third thing I tried was a complex operation with shaders (suggested by another guide) and... no results again!
1. Make sure you have the correct version of OBSE installed properly, and adjust the settings of OSR according to the OSR thread in the mods forum. If you bought the game from Steam, use the OBSE Steam version, of course.
2. Be very careful. In fact, don't trust such guides. Most of it's useless, at best.
3. Same again.
Do make sure you have the latest drivers for everything, and all the latest updates for Windows of course. And patch Oblivion correctly, obviously. The Unofficial patches for Oblivion, Shivering Isles (if you have that), and the other DLC (if you have and are using any/all of those) can help with various things. Just bugs, though.
In general, http://tesivpositive.animolious.com/ is extremely useful and informative. I suggest reading through any bits of it that are relevant to you and your situation. Can't go too far wrong there.
Hope that helps.