Safe to Compress Windows 7?

[caleg]

Hello,
I am running a Windows 7 VM on a Macbook Pro, 4 GB total. Windows 7 VM runs GREAT with 1GB of ram and with 1 Processor.

However, when I tried to compress my Windows 7 VM I had a lot of trouble booting back up. After compressing, Windows said that several files were missing and I had to insert my installation CD. The process took about 20 minutes and finally was able to boot. Then, after the boot, the VM was SLOW SLOW SLOW. I'd click, wait 10 seconds, then Windows 7 would respond. It seems the compression had some effect.

Anyhow, I'm wanting to compress again but don't want them same hassle. I don't quite understand the whole compression thing. For example, I have "auto compress" checked in the settings, however when I click "compress" Parallels says it will reduce my VM from 13.5 GB to 11.4 GB. Why isn't it already at 11.4 GB if it's "auto compress?"

Even more confusing, why does my VM say it is 16.08 GB in the Finder - then when I open it, the file falls to 14.73 GB?

Thanks!

 

[caleg]

I should add that after the VM was so SLOW, I just reinstalled the OS with a clean install. I had just installed it and was not too far in. Its back to its quick, snappy self, however I would like to save the space my compressing. Hence, I am wanting to compress but because of the poor results last time, I am leery of trying it again.

 

[joevt]

You could backup the .hdd manually before compressing so you have something to go back to. The .hdd is inside the .pvm. Right click the .pvm and select "Show Package Contents".

I wouldn't bother with manually compressing. Just use the Virtual Machine -> Configure -> Optimization -> Automatically compress virtual disks. Press the ? button for more info. Also look up "Compressing Virtual Hard Disks" in the Parallels Desktop Help menu.

Compressing is only useful after lots of files are deleted from the virtual hard disk.