Is 2 GB of RAM enough to run windows with parallels 4.0?

Yes 2GB is enough however 4GB would be better. When you launch Parallels you can tell it how much RAM to allocate for the Windows system. Lets say you split the RAM down the middle and give Windows 1GB. That means your Mac OS and Mac apps will be able to use 1GB of RAM while you are running Parallels in which your Windows system and Apps will have 1GB to use. If you are not running Windows then your Mac Apps will be able to use all 2GB of RAM. It really shouldn't be an issue though because RAM is quite cheap right now. Don't upgrade the RAM through Apple get it from a third party source like OWC: http://eshop.macsales.com/item/Other%20World%20Computing/6400DDR2S4MP/

George

It also depends on what version of Windows you will install and how much RAM you will assign to the VM. If you install XP then you need not assign more than 512 MBs. For Vista the recommended assignment is 1 GB of RAM. This is in addition to the amount of RAM Parallels requires to run. The RAM assigned to the VM is wired memory which means it is not available for OS X even if the VM is not in active use.

With XP you can get by with only 2 GBs of RAM. However, if you install Vista you will be stretching with only 2 GBs. If you plan to run Vista I would follow George's recommendation to upgrade to 4 GBs.

Windows is a magnet for viruses and malware anywhere. In Parallels Windows is running as Windows and thus is no more safe than on a PC. An XP OEM disk which should be all you need is probably less expensive and with limited RAM you don't want Vista and all the whiz bang stuff anyway.

The following may help:

Windows on Intel Macs

There are presently several alternatives for running Windows on Intel Macs.

1. Install the Apple Boot Camp software. Purchase Windows XP w/Service Pak 2 or Vista. Follow instructions in the Boot Camp documentation on installation of Boot Camp, creating Driver CD, and installing Windows. Boot Camp enables you to boot the computer into OS X or Windows.

2. Parallels Desktop for Mac and Windows XP, Vista Business, or Vista Ultimate. Parallels is software virtualization that enables running Windows concurrently with OS X.

3. VM Fusionand Windows XP, Vista Business, or Vista Ultimate. VM Fusion is software virtualization that enables running Windows concurrently with OS X.

4. CrossOver which enables running many Windows applications without having to install Windows. The Windows applications can run concurrently with OS X.

5. VirtualBox is a new Open Source freeware virtual machine such as VM Fusion and Parallels that was developed by Solaris. It is not yet fully developed for the Mac - some features are not yet implemented - but it does work otherwise.

6. Last is Q. Q is a freeware emulator that is compatible with Intel Macs. It is much slower than the virtualization software, Parallels and VM Fusion.

Note that Parallels and VM Fusion can also run other operating systems such as Linux, Unix, OS/2, Solaris, etc. There are performance differences between dual-boot systems and virtualization. The latter tend to be a little slower (not much) and do not provide the video performance of the dual-boot system.

See MacTech.com's Virtualization Benchmarking for comparisons of Boot Camp, Parallels, and VM Fusion.

Boot Camp is only available with Leopard. The Boot Camp Beta that was used with Tiger has expired and is no longer available for use. So contrary to the other poster's comment, Boot Camp isn't truly "free." You must purchase Leopard to get it.

I went with 3G so I could leave the ship memory alone and just add the 2G module.
The XP pro works fine in this environment. The new version of Parallels helped improve the performance, and I like having the linux version around to test with.
I hope this helps.
TRP