Bad news. VirtualBox version 1.5.6 eats 30-45% of cpu time when you start Delphi 2007 IDE.
The problem is related to a need for the IDE of higher timer resolution than provided by the OS (Ubuntu in my case).
According to a developer of Virtualbox:
‘Your guest uses a 1kHz timer, whereas your host probably just provides 250Hz resolution. so 1.5.6 uses a rather expensive way (busy waiting) to emulate proper timing. there isn’t much that can be done. 1.6 (whenever it’ll be out) will be slightly better, but probably not all that much. try to find out what windows app requires that 1kHz timer resolution. by default windows xp…
…just uses a 100Hz timer. ‘
Just to warn to Virtualbox + Delphi users. There’s no workaround rigth now. 
BTW, VMWare don’t suffer of that ‘problem’.
