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Parsing disk-partitioning advice

You don't read PC magazine for mutual fund advice and you shouldn't read The Wall Street Journal for computer advice.

Once again, Walter Mossberg has offered incomplete and potentially dangerous computer advice in The Wall Street Journal. The December 6, 2007 edition of Mossberg's Mailbox had a question from someone whose lone hard disk was divided into two partitions; a small C disk that was almost full and a large D disk with lots of available space. The questioner asked about merging the two partitions together. Mr. Mossberg said that Partition Magic can be used for this purpose and that it "works well."

It is malpractice to suggest changing partitions in any way shape or form without first making a disk image backup. When things go wrong, as they inevitably do, you can lose access to all the files in a partition.

I jumped on the Partition Magic bandwagon early. In the late 1990s, before the availability of virtual machines on PCs, we used it in an R&D lab to run multiple operating systems on a single computer. For years I have used it on my personal machines for a host of reasons.

Partition Magic has its fair share of quirks and problems, not the least of which is that it appears to have been abandoned by Symantec. The Partition Magic gripes at my site are consistently the most popular topic on the site.

Among the operations that can be performed on partitions, combining two of them is perhaps the most dangerous. It is more complex than resizing a single partition and is a relatively new feature. Personally, I never attempted it, both because of the risk and because there are other ways to accomplish the same thing.

In this case, I would shrink the D partition to the minimum allowable size (plus a small fudge factor for good luck), then enlarge the C partition to include the space just given up by the D partition.* Next, I would copy all the files from D to C, then wipe out the D partition and, finally, expand the C partition so that it takes up the whole hard disk.

But, before combining partitions, I would look to avoid the whole thing by moving files from the C disk/partition to the D disk/partition.

Some of the poorly chosen Windows defaults that I mentioned last time, can be tweaked to free up space. For example, the Recycle Bin defaults to 10 percent of the partition in Windows XP and System Restore claims 12 percent by default. The minimum for System Restore in XP is 200 megabytes, give it 300 or 400 and you will probably reclaim many gigabytes. Internet Explorer also consumes large quantities of hard disk space. I doubt you will notice any change if you limit the IE cache to 30 or 40 megabytes.

Windows Update creates folders in the C:\Windows folder with names like $NtUninstallKBxxxxxx$. The total uncompressed size of these folders was 245MB, 285MB and 536MB on three different Windows XP machines that I checked. These folders can be moved out of the C disk/partition, as they are used only to uninstall bug fixes. If there is a large collection of pictures, music and/or videos, they can certainly be moved to free up space. Finally, there is the Disk Cleanup feature of XP that exists for just this purpose (get the Properties of the C disk, it's a button on the General tab).

Partition Magic is also expensive. Similar software, GParted, is available for free in Linux (download from CNET Download.comor seesample screenshots). You can boot your computer using a Linux Live CD and run GParted that way. I have done this with Ubuntu and Knoppix but many other Linux versions/distributions also include partitioning software.

You don't read PC magazine for mutual fund advice and you shouldn't read The Wall Street Journal for computer advice.

* I'm simplifying things a bit. There is actually another necessary step: after shrinking the D partition, it has to be moved to the right before the C partition can be be expanded. Also, if after this shrink/resize operation all the files from the D partition don't fit onto the C partition, then another round of shrink/resize would be needed. Backup, backup, backup.

See a summary of all my Defensive Computing postings.