I found this information from on old thread on Tom's:
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No i think the only C2D it can support are the Conroe chips.
From the P/B website it says.
The motherboard built into your computer is the Packard Bell Cuba. Its main features are:
* Support for the Intel Celeron, Conroe and Pentium 4 processors in Socket LGA775.
* Supports a maximum memory size of 2 GB.
* Intel Pentium Hyper Threading technology with FMB Mainstream 2005 and 2006 support
* Intel Pentium D Dual Core technology support
So im currently looking at the E6600 or E6700.
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So looks like you are limited to the E4xxx...