I discovered on an obscure Microsoft site that if you don't disable the floppy drive in BIOS (when there is no floppy installed), the installation will either be horribly slow or will fail. I was having both.
After I did disable the floppy in the BIOS, the installation no longer failed, and went fairly quickly.
I have a SSD for my C:\Windows drive and a big disk for D: (and some other partitions). My boot times are still in the 45 second range. In contrast, I have a new install of XP Home 32 bit on a much lower power machine (Athlon X2 250, with 2 gb RAM and Seagate 7200.12), and it reliably boots in under 30 seconds.
If you will take a look (with Process Explorer or similar), Win 7 X64 loads upwards of 100 processes on start up. The bloat just gets worse.