Yes it will because I'm testing the RTM and it's a GOOD improvement from the Vista fiasco, also it behaves better that xp, I installed on Celerons(478 and 775), Pentium 4 and HT(478 and 775), Athlon 64 X2 and Phenom X4, and Core Duo, all in memory configurations of:
512MB, 1GB, 2GB and 4GB, and all were really fast even with the antivirus-firewall suite installed and office apps (openoffice).
so 7 will redeem the sins Vista made, not really for *old* cpu's, but if you have a celeron with 512MB and 40GB hard drive, that's enough for doing your office work in 7...