SQL2005 SP3 failed to install

There any many reasons that causes SP3 for SQL 2005 to fail and you can predict that by trying installing SQL2005 SP2 Security update.
One of the important reason to cause it fail: is removing the installer folder under windows or cleaning it ,so SQL Sp3 files will not continue.

This problem can be solved by extracting the SP3 files and copying all .MSP to c:\windows\installer. i tried and works without problems

Other problem related to Server SID change and this is full covered in http://support.microsoft.com/kb/925976

overall you have to check the log file and search for the reason that causes fail..

Compacting dynamically expanding virtual hard disks in Virtual Server 2005

To ensure that you get the smallest possible file size when you compact the virtual hard disk, you need to do some file system maintenance before you compact the disk. In the guest operating system of the virtual machine that is using the disk you want to compact, do the following:

1. Remove any temporary folders or unwanted folders or files.
2. Empty the Recycle Bin.
3. Defragment the disk.

Compact a dynamically expanding virtual hard disk
To compact a dynamically expanding virtual hard disk

In the guest operating system, prepare the virtual hard disk for compacting.
Open the Administration Website.
Turn off the virtual machine to which the dynamically expanding virtual hard disk is attached.
In the navigation pane, under Virtual Disks, click Inspect.
Do one of the following, and then click Inspect:
1. In Known virtual hard disks, select the virtual hard disk to compact.
2. In Fully qualified path to file, type the fully qualified path to the virtual hard disk file to compact.
3. Under Actions, click Compact virtual hard disk.
4. Click Compact.


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Caution
Compacting a virtual hard disk can use a large percentage of processor resources. We recommend that you do not perform this operation on a production computer. Compacting a virtual hard disk requires enough space to temporarily store the compacted file and the uncompacted file. This is because Virtual Server compacts a virtual hard disk by creating a new, compacted virtual hard disk and then deleting the original, uncompacted disk. If there is not enough space to complete the process, the problem is recorded in the Virtual Server event log.