Apple Hardware Test - May I download it?

I have a Mid 2007 24" iMac. After several OSX upgrades I now find that I need to run Apple Hardware Test to see if the reason GarageBand crashes when using the Master Volume Control in Chord Tuner and also why my new Squier Stratocaster USB Guiter makes no sound.

The crash report is lengthy but at the start I have the clue -

Process: GarageBand [430]

Path: /Applications/GarageBand.app/Contents/MacOS/GarageBand

Identifier: com.apple.garageband

Version: 6.0.5 (428.5)

Build Info: GarageBand_App-4280500~2

Code Type: X86 (Native)

Parent Process: launchd [162]

User ID: 502

Date/Time: 2012-12-11 21:00:45.360 +0000

OS Version: Mac OS X 10.8.2 (12C60)

Report Version: 10

Interval Since Last Report: 74422 sec

Crashes Since Last Report: 20

Per-App Interval Since Last Report: 3536 sec

Per-App Crashes Since Last Report: 2

Anonymous UUID: 3D1FC011-8F64-3E75-08B4-8742B72E8C7D

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGBUS)

Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000ed4

VM Regions Near 0xed4:

--> __PAGEZERO 0000000000000000-0000000000001000 [ 4K] ---/--- SM=NUL /Applications/GarageBand.app/Contents/MacOS/GarageBand

__TEXT 0000000000001000-0000000000429000 [ 4256K] r-x/rwx SM=COW /Applications/GarageBand.app/Contents/MacOS/GarageBand

Application Specific Information:

Performing @selector(masterVolumeSlider:) from sender MASlider 0x15701970

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread

0 com.apple.music.apps.Logic 0x01b7ab80 CSong::GInstPoint(TGInstID) const + 16

1 com.apple.music.apps.Logic 0x01a1f9c5 LgSetChannelParameter + 53

2 com.apple.garageband 0x000ed735 0x1000 + 968501

3 com.apple.garageband 0x000f2337 0x1000 + 987959

4 libobjc.A.dylib 0x040e35d3 -[NSObject performSelector:withObject:] + 70

5 com.apple.AppKit 0x04c38bd2 -[NSApplication sendAction:to:from:] + 436

6 com.apple.garageband 0x00069ac6 0x1000 + 428742

7 com.apple.GarageBandUIKit 0x030cafd3 -[MASliderCell sendActionWithCurrentEvent:] + 243

8 com.apple.GarageBandUIKit 0x030cb939 -[MASliderCell startTrackingAt:inView:] + 1129

9 com.apple.GarageBandUIKit 0x030cb10d -[MASliderCell trackMouse:inRect:ofView:untilMouseUp:] + 253

10 com.apple.AppKit 0x04c35db9 -[NSControl mouseDown:] + 867

11 com.apple.AppKit 0x04c2da21 -[NSWindow sendEvent:] + 6968

12 com.apple.AppKit 0x04c28a0f -[NSApplication sendEvent:] + 4278

13 com.apple.garageband 0x000692bb 0x1000 + 426683

14 com.apple.AppKit 0x04b4272c -[NSApplication run] + 951

15 com.apple.AppKit 0x04ae56f6 NSApplicationMain + 1053

16 com.apple.garageband 0x0019cae0 0x1000 + 1686240

17 com.apple.garageband 0x0000311a 0x1000 + 8474

It goes on somewhat so I cut this short.

I thought I would run Apple Hardware Test (AHT) but I can't find it. My iMac was puchased around the time Leopard was coming out. If I remember correctly, my iMac came with Tiger pre-installed and Leopard was on an upgrade DVD. I don't recall any grey Tiger Installer discs but they may have come with it too. Too be honest, I have so many iPod and upgrade discs from various Apple Devices I can no longer find the original Tiger installer (if there was one).

Is it possible to download AHT and, say burn it to a disc to run it. I've read somewhere that AHT can be run from a USB memory stick but I suspect that my iMac will be too old for that.

The problem existed prior to me upgrading my iMac to Mountain Lion five days ago.

Can anyone help?