Running SP1 here also on a 4 or 5 year old desktop machine. AMD 64 3500+ 2.20GHz processor with 1GB RAM. Only use the machine as a server really and to download files. Couple problems with Prevx
Prevx - Helping You Fix The Threats That Others Miss and TrendMicro but those have been sorted out.
Plan on putting it on my T60p laptop sometime (4GB RAM, Centrino Duo 2GHz) but not just yet, can't risk any downtime on the main machine.
Hopefully I'll find the time to make an image of the drive before putting on the SP, just in case anything unexpected happens.