Since the upgrade of my Media Center PC to Windows 7 I have had a few problems with fast forward on recorded TV and DVDs (which I had not seen on Vista). It was as if the fast forward button on my remote got jammed on and I could not go back to standard playback easily, it took a few seconds for the message to get through, then you ended up back where you started.
I decided it was probably a CPUprocessing speed issue, so upgrade my 3 year old AMD/ASUS single core motherboard to a current entry level dual core system, a MSI motherboard and Intel E5300 Dual Core (the brand choice was just down to what was cheap and in stock at my local supplier). This fixed the issue completely, but did require a reinstall of Windows 7, as the Intel Dual Core needed a different HAL to the AMD single core. However the reinstall was not a major issue as I run a dedicated PC as a Media Center and it is practically a default installation,