You want to deploy Windows 7 but you can't let go of Internet Explorer 6. Unfortunately, that's no longer feasible: IE compatibility problems need to be solved fast to prevent Windows 7 delays, according to recent report from Gartner.The main problem here is that many companies and ISVs coded their Web applications for IE6, which is a non- standard browser. Thus, many apps custom built for IE6 will not run on the more Web standards-friendly Firefox and Chrome browsers as well as IE8, the browser that comes loaded on Windows 7. Organizations running IE6 surveyed by Gartner reveal that 40 percent of their custom-built Web applications will not run on IE8.Despite warnings, companies are clinging to IE6 for a variety of reasons, states the Gartner report, including: the desire to minimize costs in a sour economy; ISV requirements that apps be IE6 specific; limited migrations to Windows Vista, which would have required a move to IE7.In short, organizations did not factor the time-consuming task of inventorying and fixing IE6 applications into their Windows 7 migration plans. Gartner estimates that through 2014, when all support for Windows XP ends, IE8 compatibility problems will cause 20 percent of organizations to run overtime or overbudget on Windows 7 migrations.So companies face a choice: Either spend time and money to upgrade IE6 applications so that they work in newer browsers, or keep running Windows XP.[ For complete coverage on Microsoft's Windows 7 operating system -- including hands-on reviews, video tutorials and advice on enterprise rollouts -- see CIO.com's Windows 7 Bible. ]Here is where Microsoft needs to step in and offer support, writes report author and Gartner analyst Michael Silver."It appears that Microsoft is attempting to distance itself from IE6, reversing its stance of 2001 to 2006, when it encouraged development of IE6-specific applications," writes Silver in his research note. "Microsoft must do more to help organizations with their IE6 problems that Microsoft helped cause."So what can businesses do to break free from IE6?There are several ways to support IE6 apps during a Windows 7 migration \u2014 some are temporary and some permanent, most involve virtualization, and none are perfect.Here are four ways to resolve the IE6\/Windows 7 dilemma, according to Gartner.1. Simply Fix the IE6 Applications: But It's ComplicatedFixing IE6 applications so that they are compatible with IE8 will solve the problem once and for all. But this is the most difficult solution, writes Gartner. If you have the time and money to make every app IE8 compatible, then this is the best route, but most companies do not. This method would significantly slow down the move to Windows 7, writes Gartner, which needs to be completed by April 2014 when Microsoft ends support for Windows XP, or by the time ISVs deliver new applications that don't run on Windows XP, which will likely be sooner. \nSlideshow: Windows Phone 7: Visual Tour of 10 Upcoming WP7 SmartphonesSlideshow: Seven New Windows 7 Tablets: In PicturesSlideshow: Windows 7 Hardware in Pictures: The Latest and Greatest Laptops\n\nIE8 does have some compatibility modes to run older apps, but does not have any compatibility with IE6. So in lieu of fixing and replacing all incompatible apps, there are cheaper and quicker virtualization solutions, writes Gartner.2. Run IE6 from a Terminal Server or Hosted Virtual DesktopsRunning IE6 on from a terminal server or from hosted virtual desktops are temporary ways to access the old browser through a Windows XP virtual machine on Windows 7.Terminal servers are probably the more mature and cheaper of the virtualization alternatives, writes Gartner. But these solutions can get complicated, as most users do not know how to use these technologies and are not licensed for them. Also Windows XP compatibility with terminal services can also be problematic, so Gartner recommends IT pros do their homework before they invest in Terminal Servers or Hosted Virtual Desktops.3. Try Microsoft's MED-V Tool if You Can Afford ItMicrosoft will often recommend using MED-V, its enterprise desktop virtualization tool, to resolve IE6 compatibility issues. But get ready to pay a premium, writes Gartner. MED-V is part of MDOP (Microsoft Desktop Optimization Pack), Microsoft's desktop software suite that helps enterprises manage IT environments which requires Software Assurance licensing. You also must outfit each PC with a Windows XP virtual machine.Software Assurance will cost approximately $40 or more per PC per year and MDOP costs $7 to $10 per PC per year, plus more RAM is needed.According to Gartner, early adopters have found that MED-V slows performance, causes security authentications and requires hardware upgrades. "For many organizations, the cost of deploying, running, supporting and securing MED-V on hundreds or thousands of PCs that need IE6 access is exorbitant," writes Silver in the Gartner report.Gartner concludes that using MED-V to virtualize IE seems like overkill, though if enough Windows XP applications are required by a company, MED-V may make sense for Software Assurance customers.4. Try Non-Microsoft App Virtualization Tools, But Know RisksMicrosoft has stated that its application virtualization tool, App-V (also part of MDOP), does not solve application-to-OS compatibility problems.As an alternative, Gartner points out that four vendors recently launched application virtualization tools that focus specifically on virtualizing older versions of IE6 or IE7 and making them compatible for Windows 7. These vendors are: InstallFree, Symantec, VMware and Spoon.net. But let it be known that customers may run into some pushback from Microsoft -- which recommends against these vendors' technologies because they violate Microsoft's licensing terms. According to Microsoft, IE is only licensed as an integrated part of the operating system (either originally or via updating earlier versions of IE) and IE is not licensed for use as a stand-alone feature. However, Gartner notes that it has not heard of Microsoft taking formal legal action against vendors or customers of application or IE virtualization tools.Shane O'Neill covers Microsoft, Windows, Operating Systems, Productivity Apps and Online Services for CIO.com. Follow Shane on Twitter @smoneill. Follow everything from CIO.com on Twitter @CIOonline. Email Shane at email@example.com.