If you're planning to upgrade your current PC to Windows 7 when Microsoft releases their new OS, there's good and bad news for XP and Vista users. Here's a closer look at your upgrade options.

Upgrading from XP to Windows 7

Pros: According to tech site Ars Technica, XP users can purchase a cheaper "upgrade" version of Windows 7, despite XP's version gap. (Normally only users who purchased the latest OS get the cheaper upgrade option.)

Cons: Windows XP users will have no direct upgrade path. That means that in order to upgrade to Windows 7, you'll have to do a fresh installation of Windows 7 and manually migrate your files and apps to Win7—so you'll want to make sure to back up XP before upgrading or just dual boot XP and Windows 7.

Upgrading from Vista to Windows 7

Pros: Unlike XP, Vista users do get a direct upgrade path to Windows 7, so your files and apps should migrate to Win7 without any problems. (You should always backup before upgrading to be safe, and just to hedge your bets, you may also still want to dual boot Vista and Windows 7 rather than installing Windows 7 over Vista.) Vista users will also get the cheaper upgrade price.

Cons: It probably won't affect most users, but the Vista-to-Windows-7 upgrade paths are actually limited by version in the following ways:
Windows Vista Home Premium to Windows 7 Home Premium
Windows Vista Business to Windows 7 Professional
Windows Vista Ultimate to Windows 7 Ultimate

If you don't follow one of those three upgrade paths, you'll have to perform a fresh install.
Be sure to check the Ars post for a more detailed rundown of the differences, including a discussion of the fate of your Windows Vista Ultimate Extras.

Upgrading to Windows 7: what XP and Vista users need to know