Parallels 5 slows Mac it's almost unusable

Well it sounds like you need more RAM, so why not just upgrade?

 

I have had a problem running under multiple processors. Set your processor usage to a single processor. This was an issue some tima ago, and I don't think it has really been addressed sufficiently. I have about 35 to 40 Parallels installations around my network, and I set them all to a single processor for this very same reason. It helped tremendously.

Don't bother talking to support about it, I went through a long series of conversations with them via email, and they won't even admit there might be a problem here, although I think they know there is.

 

I was having similar problems. A few things have helped.

1. Empty temp file directories in windows
2. If you have parallels doing automatic snapshots, see how much space they are taking up. Mine auto snapshots were taking up over 100gbs of space and my disk drive was running out of space I ended up deleting them all. Getting rid of the snapshots sped up my system considerably.

 

I learned from VMWare's support docs that portable Macs tend to turn off one core if the processor becomes too hot. Since the cores usually are quite busy when Parallels is running, the processor will soon shut one of them off - this then means that a) Windows thinks there are 2 cores but only one of them is running, b) that single core must then carry out the work on both the Windows *and* the Mac side. That significantly slows down things.
However, having just one core running for Parallels / Windows helps the Mac keep a cool head (or rather processor).

 

I am having the same problem> Help!!!!!

 

What? With the cores getting to hot, being shut down and thus your machine runs slow?

Well, then, perhaps you should define your configuration and ask about keeping your cpu (cores) cool.
That should be new thread onto itself.