can you look at your dial up and modem connection settings to see if it is set to reconnect automatically?

or if IE the connection settings are there too.

I know when I had dial up there was a area where we could set it to redial automatically and hold the connection longer to avoid time outs?
places to look-
control panel = modem - network- dial up - connections

I have reinstalled xp or I think is a setting to fix- for missing files ect- maybe that is all you need to do.
If you do reinstall- then just click for all the updates since then

that's how I did it just a couple months ago.

but try to check all the settings first.
or you might be able to just search the XP CD for that missing file??