You'll have to provide some more information before we can venture an opinion. On my XP the activity looks like this, and I think that's how it should look -
Download Process Explorer from SysInternals and have a look at the activity for mfevtps on your machine. It only has 6 threads on mine, and they show no CPU activity, but on yours you should be able to see which thread(s) have a high cpu usage.
Then post back and tell us your OS and version, what McAfee program you have and what version, and whether your OS and McAfee have the latest software updates. Also check that the program is running from the system directory, that it can be verified in Process Explorer as a McAfee file, and that in the Services tab only one McAfee service is listed.
I assume you've already run an AV scan and are not running any other anti-virus software alongside McAfee.
There have been reported cpu and memory problems with this process in the past : here is some advice from searchtasks.answersthatwork.com :
Mfevtps.exe Description :
McAfee Process Validation Service. Background service installed by McAfee security products such as McAfee VirusScan or McAfee Internet Security. This background service watches over all the McAfee resident protection programs and prevents other programs or the Task Manager from terminating them. The aim here is to protect your McAfee security software from unauthorised intervention by a virus or other malware as, in order to properly infect your PC, viruses and malware programs often attempt to shut down your antivirus or Internet security software before trying to infect your PC (so that the infection can be more thorough). The role of this background service, the Process Validation Service, is to prevent just this from happening.
Mfevtps.exe Recommendation :
This is an essential security component of your McAfee security software - Leave alone therefore.
Note, however : On some PCs this process sometimes hogs the CPU, consuming as much as 5% to 10% of CPU resources. If you believe that your PC is unreasonably slow then do a manual update of your McAfee software, follow that with a reboot, try uninstalling McAfee and re-installing it, and if you still have the problem then open the McAfee Control Center and disable ACCESS PROTECTION - this will tell this background service to stop watching over McAfee programs and may solve your PC performance problems.
This background service can use anything from 4Mb to 25Mb of memory.