As the computer is a Compaq I would be much more suspicious of the hardware having problems than it being win7. I have a netbook (which is waaaaay worse than your new laptop) with win764bit and 1GB of ram, and it does not take 3min to load. It has to either be a setting, or a hardware issue.
If while installing XP you had deleted the partitions, made a new one, and then reformatted the new partition you would (or at least should) not have any installation issues. The 'at risk' error may be due to the BIOS if there is any BIOS level protection from changing the OS (but I thought that was only on Intel chipsets, not AMD), so check your BIOS settings and see if there is anything in there that may prohibit modifications to your system drive.
HP support is a joke at best, and always has been. Remember all those people were told they were loosing their jobs just a month ago. I would bet that they are a little less than willing to give good customer service when they have a company that treats them like that. Also, they will not provide support for any software or hardware that did not come with their system (eg, you are on your own with XP).