Finally solved: Dubious lan-driver package. This "ancient" grandchild-pc needed repair, so grandpa said he would fix it. Mobo manufacturer only had xp-drivers available, whereas win 7 was wanted by grandchild. So I used the xp-drivers from mobo-site, installed in compatibility mode, and all installed ok and accepted as valid. Device manager seemed fine. But I was fooled by this, 100 % cpu-usage ! Uninstalled the drivers, and cpu-usage back to 2 %. Found other drivers somewhere else, and now all is fine and running at 2 % usage. Will absolutly avoid compatibility mode in the future ! Clean install win7-ult from MS-orig dvd. Activate with DAZ. After a loooong process of updates, driver installs etc., all seemed fine. BUT: Processes under taskmanager show 100 % cpu load just standing idle in desktop !! Tracked this down to the service "eventlog". Disable eventlog-service via msconfig, fresh boot, and and all is well (just 3 % cpu load). Tried clearing all eventlogs, did not help. But, after a boot with eventlog disabled (via msconfig), and THEN enabling/starting the eventlog-service, I did get 3 % load. Dont understand this at all. Why the different behaviour of booting with the service enabled, vs starting the service AFTER boot completed ? Any clues ?