What you want to do is setup and configure Windows 2000 Clustering. There are very specfic steps that must be taken to accomplish this task and there are many 'White Papers' written on how to do these.
One key item, in a Windows 2000 cluster you have 2 boxes sharing a single storage array (this provides failure of the hardware and local software, but does not provide failover of the databases). If your current environment is not setup for this then it will be very pricy to advance to this stage.
Legato carries application software for Stand-by server, replication between servers, co-standby, offsite, etc.
Clustering either with straight Microsoft or using a 3rd party product is very advanced. My recommendation would be if you areunsure how to proceed than contract this out to a firm that has performed these steps and knows what to expect, when to expect and how to keep the wheels in motion (troubleshoot).