There are actually (at least) three ASCOM drivers appropriate for the RCX400.
One is Ajai Segal's "beta" drivers, written with the "assistance" of Meade
(they loaned him an RCX400, and provided some access to the firmware authors).
The most current version of that is 4.2.12 , and is available as the file
"MeadeRCXSetupV4212RC2.exe" from the ASCOM-Talk Yahoo group's Files area
(not the ASCOM 5.01 download page cited by Ron). There is also a copy (along
with the 4.2.6 beta 6 edition) in the Files area of the RCX400 Yahoo group.
http://tech.groups.yahoo.com/group/RCX400/Ajai stopped working on the driver when he encountered RCX firmware issues
involving the precise control of the focuser. Meade has not released RCX firmware
updates to correct them, so it's in limbo.
The site Ron pointed to is where you can get the current -released- (vs beta)
version of the LX200GPS driver, which works perfectly well with the RCX400.
You will not have access to the numerical millimeter level of control of the focus
mechanism, but for all other scope control operations, the LX200GPS driver is
the way to go.
What i'm not sure about is where the 5.01 ASCOM driver falls into relationship with
the development stream of the LX200GPS driver. The "released" LX200GPS driver
under the v4.1 era of ASCOM was roughly v4.1.12 (yes, the "12" is confusable with
the RCX's "12"). But Jon Brewster continuously upgraded the LX200GPS driver,
and it was at v4.1.28 ... available in the JonBrewster folder in the ASCOM-Talk
Yahoo group's Files area. I -think- that he would have used that as the basis for
the v5.0.1 version at the Official ASCOM download site(s) cited by Ron:
http://ascom-standards.org/Downloads/ScopeDrivers.htmFor the most "bug-free" experience, use the LX200GPS driver.
If you wish to have remote control of the dew heater, etc, experiment with Ajai's
RCX-specific driver... but it does have raw edges.
have fun
--dick