It's an uphill battle. Drinking water isn't too bad because it hardly leaves any conductive solid residue, but it's still bad. You need to let all the components dry out. Open the case, use a blow-dryer for a few minutes (not too close, you don't want the air pressure to damage the components), then let everything rest in a warm, dry place (e.g. a shelf above a radiator) for a few days. (Yes, days. Small drops of water tend to remain in inaccessible corners and can take a surprisingly long time to come out.)
The hard disk is especially vulnerable: it's very fragile and has an especially large amount of inaccessible places. If it was in the way of the spill, you'll probably have to write it off. If you need to recover data from it, professionals might be able to do it, but it's very expensive. You have two choices. You can hope that the water only got into the electronics, not into the heads; let it dry, and if it doesn't work then, throw it away. Or you can decide right now you'll pay dearly to get the data, and then keep the disk wet: drying wet hard disk heads is likely to be the final blow that kills them.
See also Water damaged parts, is there any chance of recovery?, My server room has flooded.