For the ones who dont know:

S registers are memory locations in a modem
where settings are stored or status information can be examined.

Modems can have dozens of S registers, while only the first dozen or so are standard.

S registers are set by issuing ATSN=xx to the modem.
N is the number of the register being set,
while xx is the value the register is set at.

For example,
the register S0 determines how many rings required before the modem will answser in Auto Answer mode.

Some Good Registers to play with are:

S7:
Sets the amount of time the modem will wait for carrier upon dialing. Measured in Seconds, default := 60

S10:
Sets duration that the modem waits to hang up after loss-of carrier. If you find your modem hangs up too easily if: for example, someone picks up the phone, then I'd suggest changing this value.
Measured in 1/10 seconds, Default is 7, I use 50.
If you set this vaule to 255, your modem will not hang up due to loss of carrier.

S11:
This is gold, It sets the duration and spacing, in milliseconds, for tone dialing. You can greatly increase dialing speed with this setting.
The default is 70, I reccommend 45.

There's lots more, but they're no fun. If anyone wants them posted, then just say so.

In order to apply these setting in windows:

The dialing string is found in the registry under:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Modem\0000\Init

The entry is named "2"
The 0000 is the modem number, On mine it's actually 0001

Just paste the settings you want on the end of the setting before the <cr> closing statement,

if you can see somewhere in the string that other S registers were initialized, then stick it on the end of those.

For example: Mine is AT&FE0V1S0=0S10=100&C1&D2+MR=2;+DR=1;+ER=1;W0<cr>

It originally was:
AT&FE0V1S0=0&C1&D2+MR=2;+DR=1;+ER=1;W0<cr>

I was sick of getting disconnected, so i pasted S10=100 on the end of S0=0.

Remember, not all modems listen to all registers.
Mine didnt listen to S11 dammit, But my fathers, and cousins did.

This always works on U.S. Robotics modems.