AutoCAD 2005; cannot use part menu

[ktanaka_ssktanaka]

Hi,

I'm using AutoCAD 2005 Mechanical Desktop.

I'm in trouble with the sudden stop of a function which I could use before.

The [part] menu disappeared and cannot use some related commands like 'convtosolid'.

I tried re-install the whole software but it didn't improve the situation.

Is there something to be configured or softwares to be installed to utilize [part] related functions??

I'm waiting for your suggestions.

regards