I don’t know about 4.5, but in 4.1 there wasn’t many option to
TechTool saved me a couple of time in the past, but it’s damned slow.
If you purchased AppleCare for your Mactel, there is a version of
techtool in the package, but I think it’s lighter than the commercial
version. If you didn’t purchase AppleCare, it may not be too late…