Ask DACS
April 2012
Moderated and reported by Jim Scheef.
Q – By email: I am looking to show DVDs on my TV. I have an old tube TV with RCA input and output connectors as well as an S-video port marked input on the TV. (1) What equipment would work to feed from my windows 7 pc to the TV? (2) Will it also work to output to the PC?
A - Despite the fact that the questioner was not at the meeting, this generated a lot of discussion. Unfortunately, without some information about the Win7 PC, everything was speculation. Based solely on the information provided, the consensus was that a new television would make the most sense. Nearly all modern televisions have both multiple HDMI plus a VGA input which would work with just about any computer. Other than the assumed VGA output, we do not know if the PC has other outputs. Some modern laptops have dropped the VGA connector and replaced it with either DVI or HDMI. Modern desktops often have similar connectors. Many older video cards have an S-video output. I guess we would not have the question if it were that simple. Many people suggested replacing the video card with a high-end video adapter that has both performance and the HDMI connector to support good video. Of course that would work with the tube-type television in the question. So far we have not discussed sound at all. Only HDMI supports both video and sound; all other video connections require a separate sound cable (digital) or cables (analog).
The simple answer to Part 2 of the question, given our lack of information, is "no". For the TV to send video to the computer, would require video (and sound) outputs and the computer would need a video card or device for video capture. Video capture is a whole topic unto itself. There are external video tuners that connect to the computer by USB. One member recommended devices from Hauppauge (hauppauge.com/).
Q - I've heard that the Windows registry is made up of more than one file. Is that true and where are they stored?
A - The registry is, indeed, made up of several files. The user portion is found in the USER.DAT file located in the root of the user's profile directory and contains the HKEY_CURRENT_USER (HKCU) hive. In Win7 this is in C:\Users\<username>. In WinXP it was in C:\Documents and Settings\<username>. The machine or system registry files are stored in %SYSTEMROOT%\System32\Config where the "systemroot" variable contains the Windows directory name (C:\Windows, C:\WinXP, etc.). For more information search on the Microsoft website or read the Wikipedia article (tinyurl.com/btlekp2). You can see the size of the user profiles on a machine (all of the user-specific files on a machine, including the registry) in the System applet in Control Panel. Click the Advanced tab and then the button in the User Profiles section.
The registry is a hierarchical (as opposed to relational) database. Because the pointers from parent to child keys and values are build into the structure, this form of database is normally very efficient. Efficiency, and thus speed, suffers as the database grows and new keys and values are entered over time.
Q - I want to make a backup of my computer, a Power Mac. When searching for a backup program I see the terms "copy" and “image" (sometimes "disk image"). What do these mean? How are they different? And why would I want one or the other?
A - On a Mac there is a file format called DMG. Files with this extension are often used for software distribution on the Mac because they are treated as if they are an entire disk. It can contain anything from an entire hard drive to a single folder with a single file. When opened, the "disk" is mounted and individual files can then be copied to or from the DMG disk. DMG files are created using the program called "Disk Utility" included with Mac OS X v10.3 and later ("Disk Copy" in v10.2). The file format includes compression to reduce the size of the "image". These files are often used in the same manner as ZIP files on a PC. There are several common programs used to back up the entire hard drive of a Macintosh. One is called "SuperDuper" ( http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html) and another is "Carbon Copy Cloner" (www.bombich.com). Both can make a fully bootable copy of a Mac hard drive on an external drive. In this context there is no difference between a hard drive backup copy and a hard disk image. For normal backups, Mac OS X includes the program "Time Machine" (starting in v10.5, the last version to support the Power PC) which makes hourly incremental backups to a designated volume. To the question of "image" versus "copy", the difference has become nothing more than semantics (see below for more on this). Forget which word is used and look for the features you want for convenience and recovery. [Some of the discussion was inaudible on the recording.]
Going back many years in the PC world, a "disk image" meant a sector by sector copy of an entire hard drive, including empty sectors. Thus an image (a true image) of a 100MB disk (large in those days) would be a file slightly larger than 100MB even if the disk contained only a few files. The other type of backup was a "backup copy" which copied each directory and file to a tape drive or some proprietary file format. Thus a backup of a hard drive with only a few files could be very small, even smaller than the space the files occupied on the original disk as inter-file gaps were eliminated to save space. Compression allowed for even smaller backup files or (more commonly) allowed packing more files onto a single backup tape. Again going back to the early years, the disadvantage of an image backup was that it was not possible to restore an individual file. Restoring the image to the original disk guaranteed the disk would be bootable but overwrote every file because it was returning every sector to the exact same state it had at the time the image was made. The more common "backup copy" allowed for restoring individual files but was more difficult to use to restore a machine from the "bare metal". Over time imaging programs learned to skip empty sectors making such disk images smaller than the source disk. Today the difference between an image and a copy has blurred in products like Acronis True Image Home (tinyurl.com/5hh5v) which is still available at user group prices from our old friend Gene Barlow (ugr.com). This product and others like it allow the user to make an image (full backup) and then incremental backups of just the changes. An interesting development is the ability to use VHD (virtual hard disk) files which is the same format used by Windows Virtual PC. If I'm reading the Acronis website correctly, a VHD file should be bootable under Virtual PC.
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