How to find recently installed stuff?

WINXPsp2

I'll be away from the computer for a few days & when I fire it up it's either acting weird or has lost several hundred MB or doesn't "feel" right.
Typically, some other (teen) family member has done the forbidden and touched MY computer.
Is there a way to find out what goodies have been allowed into my private domain?
I've tried Add/Remove & it finds some things, but I assume if the program or whatever doesn't make Add/Remove a part of it, it doesn't show here.
I've tried Start>Search and plugged in the suspect dates, but the option is "modified". Would this also indicate items that were newly plugged in somewhere?
I've tried keeping a list of Processes & Startup items and comparing pre-problem to post-problem with limited success.
Any Geek tricks to monitoring what goes on the hard drive while I'm out slaving to make a dollar to pay the overpriced ISP?
Thanks!

 

I personally do not know of any free applications that will show these especially if they have been uninstalled.
you could try "system restore"and see if it returns to a good state.
If that does not work then you could always go through our cleaning procedure.
It seems a bit laborious but you will end up with a pristine PC and then PROTECT your PC with a PASSWORD!!!!!!!!!

http://forums.majorgeeks.com/showthread.php?t=35407

 

Thanks for the reply.
I've just finished getting rid of some 1.4GB of crap that I could easily find.
I sweep & clean about every 10-14 days, basically following MG recs.
I had some problems in my early "I know it all" pc attitude with System Restore and now rely on it only in emergencies. (Please, no comment on this. I probably shouldn't be allowed to own a computer.)
Passwording is a good idea, but there are times when a legitimate reason crops up to let the outsiders in. Maybe I'll be a bit more resolute about frequently changing it.
I was only wondering if there was some built-in way to see what had changed while I was out.
Thanks again!