I just installed Freya on an old Pavillion Slimline with a Pentium E2140 Dual Core 1,6 Ghz, 2GB of RAM and a Radeon HD2350.
I know it's not the ultimate state of art PC, but I thought it was enough for Elementary OS and Pantheon DE, which I found amazingly fast on just slightly better machines. But in the end I found myself with an incredibly slow OS, not usable at all. System animations take forever to end, I disabled animations with elementary-tweaks but they are still taking the same time. Scrolling on the browser is sluggish and watching a YouTube video is impossible since it hardly displays a couple of frames a second.
Seems to me a graphics card issue, but the system doesn't show me any proprietary drivers available to install, and (in Info) is perfectly able to tell me what card I'm on, so doesn't seem to me like I'm using generic drivers or something.
The processor supports 64-bit, so I installed the 64-bit version, may this be a problem?