You could call Microsoft, prove you have Genuine Windows via License Key Number on the Windows CD Case or computer sticker, and ask them to mail you all the service packs for your OS. They should say yes and mail them to you for free.
All the other updates, some of which are not critical and/or drivers, download them and burn them to CD or save them on some storage medium. Update in bulk as necessary.
Other than those, you could try burning all the system updates to CD manually. Or, perhaps copy updates by making batch files in command lines, but that may take longer.
These are only a few suggestions.