Fair enough... I think my concern is that there can often on an XP based platform (older) PC* be driver issues if one tries to run 7 on that same machine. I will admit this can be a great obstacle w/ HPs than Dells. I have, also, change PCs from XP to 7 but, used the & Upgrade Compatibility Tool to 1st investigate rather than check the manufacturer's web site. Indeed, the 4600 is not on Dell's list of Dimension models that they say will support 7. On the other hand it is true that it can be surprising, almost amazing what hardware 7 will run on, regardless of how well. It's know to run on, say, old P3s w/ as little as 256 to 512 RAM. IF 7 can find all the driver's it needs, well than... enjoy.
* A Vista machine to 7, the platform isn't in a completely different family, so to speak. XP to 7, that is not the case... hence why Upgrades from XP to 7 are not possible but, Upgrades from Vista to 7 are. But, if as a custom Install, it finds all it's drivers then, cool.
Cheers,
Drew