Just be aware that the new tracing function requires 800 Mbyte extra space on the C drive (default installation).
If you want to relocate the ISA tracing files, do the following (thanks to Jim Harrison):
A) Add the following registry value under HKLM/Software/Microsoft/ISATrace
Value name == AlternateTracingFile
Value type == String Value
Value data == <FullPathToTracingFile.bin> (e.g. "D:\Windows\Debug\isalog.bin")
B) Add the following registry value under HKLM/Software/Microsoft/ISATrace
Value name == UseAlternateTracingFile
Value type == DWORD Value
Value data == FFFFFFFF (hex)
C) Restart your Server
D) Delete/Archive the old isalog.bin and isalog.bak files unter %windir%\debug
If "UseAlternateTracingFile" = 0, "AlternateTracingFile" is ignored.
If "UseAlternateTracingFile" = FFFFFFFF, "AlternateTracingFile" is used (if valid and permissions allow).
For more info, check out http://www.microsoft.com/technet/prodtechnol/isa/2004/plan/sp2.mspx.
Service Pack 2 includes an error-level tracing mechanism that operates continually in the background. If necessary, the tracing information is available for Microsoft Product Support Services. The tracing mechanism does not collect personally identifiable information.
Tracing takes place in the background, and has a negligible affect on ISA Server performance. A 400 megabyte (MB) file (%windir%\debug\isalog.bin) is created by Service Pack 2 on each computer running ISA Server services, to contain the tracing information.
We recommend that you use the default settings for this feature. However, if you want to modify the tracing mechanism, you can do so through the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ISATrace. To change the size of the file used by tracing, change the value of CircularlLogSizeMB. To disable tracing, change the BootTracing value to 0. This does not delete the file, which has to be deleted manually. After registry changes, restart the computer so that the changes take effect. If you create the registry key before installing Service Pack 2, and set the BootTracing value to 0, the tracing file will not be added during the installation, and tracing will not be enabled.