Upgraded to 4 and performance isn't what I'd hoped for I've just upgraded to 4 but it seems slower. Running Vista Biz on my old Macbook Dual Core seems far more choppy than on 3. I've checked the device manager and everything seems fine. Is there something else I should be enabling/disabling? I'm running in full-screen.
Make sure that there is enough RAM on the Mac side (Apple -> About this Mac). Minimum requirements for Parallels 4.0. is 1 Gb of memory. This is the main reason why Parallels 4.0 might look slower than 3.0. Another case is Parallels Tools. First, they have to be installed, second - installed fully. To make sure, just uninstall them from Add/Remove programs and install back. Also, make sure that there is only one antivirus currently installed, if there is more than one, that may cause the conflict and/or slow performance.
I've managed to improve matters by changing the config. I changed from favoring battery to perf. However, there are still some frustrating issues that seem to stem from either the host or the guest moving into screen savers or going to sleep. Parallels is then very unresponsive and can get very confused. E.g. couldn't get Vista to leave it's screen saver without changing from Full Screen to Window. Also can you please do something about that huge top bar in Window mode, it takes up a huge chunk of the screen for no reason.
