Software updates that used to take a month to deploy are now completed in one day. Weiszhaar doesn't need to first perform regression testing on the application, produce a distribution package and test it. "Within five minutes we can deploy it to every single person in the company," he says.

SoftGrid doesn't work for all applications, however. In some situations, virtualized applications won't interoperate unless they're either packaged together or one is installed locally, Weiszhaar says. Because of interapplication dependencies, he doesn't virtualize Microsoft Office. (Softricity co-founder and Vice President David Greschler says SoftGrid's latest release supports all application components except for NT services.)

Determining application dependencies and sequencing apps to meet Suncor users' needs also required extra work, Weiszhaar says. "For each application, you have to ask, 'What am I losing, and what am I gaining?' " he says.

Stream Theory claims to offer application environment virtualization that's more flexible. AppExpress lets the administrator specify which DLLs or other application components can be virtualized and which need to talk to one another, says Chief Technology Officer Arthur Hitomi. The software won't, however, allow incompatible versions of an Oracle or Office application to run simultaneously, as Soft-Grid does.

On-demand streaming tools can also manage and update applications or system images in a Citrix Presentation Server or Terminal Services server farm. Suncor uses MetaFrame to provide thin-client access to applications that point to its back-end databases, but in the past interoperability conflicts forced Weiszhaar to dedicate separate back-end servers for applications that misbehaved.