The point Jax was making is that Windows 8 might be a system hog in terms of ram. Something around 1gb devoted solely to the OS would not be out of the realm of possibility. I have Win7 myself, with 4gb, and I do fine for ram, but I don't know how different Win8 is.
If you are having dificulty with altctrldel when it brings up the task manager straight away, you could try changing the setting (I forget where it gets changed, but google will know) so that instead of the TM you get a bunch of options. One of which is the TM.
There is also an option in the TM "Always on Top". You could try using that.
EDIT: All you need to do is delete the FO3 and TTW stuff from your FNV data folder; ESMs, ESPs and BSAs.