Dell has Vista 64 bit drivers so it will work with 64 bit OS.  However, do your homework before installing Windows 7.  Dell has Vista drivers but NO Windows 7 drivers, but the Vista drivers usually work OK in Windows 7 since Win 7 is basically "Vista Improved".  When you install Windows 7 64 bit you will have to do a complete new install as you can't use an "upgrade" version since you are going from 32 bit to 64 bit.  You will also have to install all your programs so make sure you have the full programs with the installer.  Backup your user data to CD/DVD's or an external hard drive or a USB flash drive.   Many that are upgrading to a different operating system keep the current hardrive and Operating System and buy a new hard drive to install the new OS on.  This gives them a "fall back" in case it's needed and also doesn't require backing up user data since the drive isn't being touched.     Windows 7 will install most of the needed drivers however, in most cases you must use the Dell sound driver as a non-Dell sound driver will either not work or not work correctly. 
I'd like to purchase 64 bit version Windows 7 and move up from the 32 bit version of Vista Home Premium that I have now, however some people don't believe the E6550 Core 2 Duo is compatible with 64 bit systems. I'd like to find out prior to making a purchase.
Can a 530 with a E6550 processor run compatible with a 64 bit Windows OS?