The pages on the support site seem to be missing, so here's the links straight from Microsoft:
Download the Debugging Tools for Windows
Current Release version 6.8.4.0 - October 18, 2007Install 32-bit version 6.8.4.0 [16.7 MB]
Previous Release version 6.7.5.1 - July 3, 2007Install 32-bit Beta version 6.7.5.1 [15.8 MB]
Previous Release version 6.6.7.5 - July 18, 2006Install 32-bit version 6.6.7.5 [15.2 MB]
Previous Release version 6.6.3.5 - January 24, 2006Install 32-bit Beta version 6.6.3.5 [13.8 MB]
Previous Release version 6.5.3.8 - August 10, 2005Install 32-bit version 6.5.3.8 [13.0 MB]
Windows Vista SP1 RTM symbols
These packages contain the full set of symbols required to debug
Windows Vista SP1 RTM.Note: These packages also contain
the full set of symbols required to debug Windows Server 2008 RTM.

• Windows Vista SP1 RTM and Windows Server 2008 RTM x86 retail symbols, all
  languages (File size: 267 MB - Most customers want this package.)
• Windows Vista SP1 RTM and Windows Server 2008 RTM x64 retail symbols, all
  languages (File size: 216 MB)
• Windows Vista SP1 RTM and Windows Server 2008 RTM x86 checked symbols, all
  languages (File size: 240 MB)
• Windows Vista SP1 RTM and Windows Server 2008 RTM x64 checked symbols, all
  languages (File size: 217 MB)

Windows Vista SP1 RC1 symbols
These packages contain the full set of symbols required to debug
Windows Vista SP1 RC1.

• Windows Vista SP1 RC1 x86 retail symbols, all languages (File size: 267 MB - Most
  customers want this package.)
• Windows Vista SP1 RC1 Itanium retail symbols, all languages (File size: 151 MB)
• Windows Vista SP1 RC1 x64 retail symbols, all languages (File size: 215 MB)
• Windows Vista SP1 RC1 x86 checked symbols, all languages (File size: 240 MB)
• Windows Vista SP1 RC1 Itanium checked symbols, all languages (File size: 190 MB)
• Windows Vista SP1 RC1 x64 checked symbols, all languages (File size: 215
  MB)

Windows Vista RTM symbols
These packages contain the full set of symbols required to debug
Windows Vista.

• Windows Vista RTM x86 retail symbols, all languages (File size: 250 MB - Most
  customers want this package.)
• Windows Vista RTM Itanium retail symbols, all languages (File size: 141 MB)
• Windows Vista RTM x64 retail symbols, all languages (File size: 196 MB)
• Windows Vista RTM x86 checked symbols, all languages (File size: 231 MB)
• Windows Vista RTM Itanium checked symbols, all languages (File size: 178 MB)
• Windows Vista RTM x64 checked symbols, all languages (File size: 209
  MB)