I've just done a quick test and I fear it's not as simple as that, Grazie.

Each Filter Package is stored in C:\Program Files\Sony\Vegas 7.0\Presets\FX Packages\{long unique ID in squiggly brackets}\filtername with a .sfv file extension.

The {long unique ID in squiggly brackets} appears in the registry in the following:

HKCU\Software\DirectShow\Presets\FX Packages\{long unique ID in squiggly brackets}

as well as HKU\{Unique User ID}\\Software\DirectShow\Presets\FX Packages\{long unique ID in squiggly brackets}

and has a number of keys associated with it.

I suggest you check out if the registry entries are there. If so, then my guess is that copying those files back should simply work. If not, the keys in the registry (at least on my system) are:

(Default) REG_SZ (value not set)
Flags REG_DWORD 0x00000002(2)
Name REG_SZ TestFilterPackage
Stream REG_SZ C:\Program Files\Sony\Vegas 7.0\Presets\FX Packages\{long name in squiggly brackets}\TestFilterPackage.sfv
Type REG_DWORD 0x00000005 (5)

Replace TestFilterPackage with your filter name in both cases and {long name in squiggly brackets} with the proper string.

Remember, this is ONE set of keys PER PACKAGE, so this could be somewhat tedious.

Normal caveats apply as regards registry editing (ie I take full responsibility for providing you with enough information to render your PC inoperable, but not for you actually making use of that information)

Hope this helps.

Tim