Hello Bondy:
It looks like everybody is on the same page, I would just like to add one caveat here. It sounds to me like you're talking about DDR 333, and DDR2 800 you cannot use DDR2 in a board designed for DDR. As far as I know the fastest memory in DDR is 400 MHz.

As far as using faster memory of the type the board is designed for I agree there should be no problems. Also all memory is not created equal, that is higher quality memory has different internal timings wait states etc. that can improve performance over memory of the same speed, I've recently upgraded 2 computers with DDR 2 one with 800 megahertz memory that was rated for 667 and the other with 667 that was rated for 533. Basically in one computer I use what I had on hand, and in the other I used what was on sale.

Both computers experienced a slight increase in performance on memory benchmark test, the first was upgraded with high-quality memory that I had on hand, the second was a sale memory. I'm going out on a limb when I say that had the 533 memory in that computer been high-performance, I might've actually lost some on the benchmark tests replacing it with the on sale 667 MHz memory.

just something to think about , most bios will automatically set up to the memory's internal timings, with the bus speed limited by the board at least theoretically you could put faster megahertz memory in and end up with reduced performance, that is if you're using cheap economical memory.

Memory manufacturers are a sly lot, you can slow down the internal timings and run at a higher bus speed with cheaper memory chips, or is I recently found out when I purchase some high-performance DDR2 8500 1066 MHz memory , the manufactory was actually using chips designed for 800 MHz, it kept respectable timings and raise the voltage from 1.8 to 2 V ,it performs as advertised but don't even try and overclock it it's at its limit. As I said thay are tricky.

PS: I bought four gig of 667 memory for $37, in 1989 I paid $220 for four meg of memory, if anybody's got a time machine we can get rich.