That's what I was afraid of. I dreamed all night of waking up to find a spectacular workaround detailed here in reply to my query, but I guess it's not to be. Oh, well.

So, keeping in mind my relative newbie (at least to hackintoshing - I'm a longtime Mac user and fairly computer-literate) status, what would you suggest as far as a way forward? And, on a related note, how would I go about (or is it even possible?) creating a snapshot of my current setup so I can restore it if my upgrade attempt goes haywire?

Thanks again for your help.

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Toshiba Satellite L505-S6954 Laptop
Intel Mobile Core 2 Duo T6500 @ 2.10Ghz
Intel GM45/GM47 Chipset
Southbridge Intel 82801M (ICH9-M)
4GB DDR2 Memory
Mobile Intel GMA 4500MHD
Dual-booting Win7 and OSX 10.5.5