The "problem" is that the BIOS is custom proprietary which means each model has its' own BIOS and does not offer the "FULL" CPU support list for more than a handful of "production" HP Compaq Presario configurations. In simpler terms each CPU MUST be part of the BIOS otherwise it may not run or at best be "dummied" down if not recognized by the BIOS.
Mine runs 800mhz Presario CQ62-119WM I think it is. Any how check this out, Mine is the Celeron 900 and compared to the T4400 its almost a match: http://ark.intel.com/Compare.aspx?ids=42925,41498,40739,
I could not find an exact match {USA} anyway, and I would recommend that you use the same CPU as you already have for the reasons stated above, otherwise you can "TRY" a different BIOS for a similar model - but other BIOS may be locked-out.
Notebook & Production PC {Dell, HP, Gateway, etc} are ALL proprietary and very-very specific to components; it is nothing like a home built PC with a MOBO that will support 20+ CPUs.
oops, CQ62-219WM not 119WM. Anyway, I bought a T6670 and am gonna giver her try. I found that I can use a T4400 though with my bios. T4400 and T6670 almost identical, only difference is a added feature, can't remember.