Computer monitoring software?

Is there any type of software that can monitor your PC to where you can view what activity has been going on? I leave my PC on at all times. Somtime's when I wake in the mornings. It seem's like somthing has changed. I am just trying to find out if my computer has been hacked. Is there anyting out there that can do that? Thank You

 

Only thing I can think off is pc anywhere program but that has to be installed on both computers and its not free either. The other is remote assistance through windows XP but that has to be accepted on the other computer.

Hope this Helps

 

not sure about the monitoring software but...
If you think your PC has been compromised you could check every thing and at the same time do some prevention hear is a list of the Major things I do to all computers on the network

1. Make sure the Windows is up to date
2. Make sure the anti-virus, AD Ware and firewall are up to date and run a boot scan
(boot to the AV then do the 1st scan)
3. Make sure any rules I have made in the fire wall are still valid and add or delete as needed and close any ports that don't need to be open
4. Check Event Viewer in Windows (Admin Tools)
5. Change My pass words for all PC's on network (NON DICTIONARY WITH NUMBERS, LETTERS AND SYMBOLS UPPER AND LOWER CASE AND AT LEAST 10+ CHR LONG this will force them to find an exploit)
6. Change router pass word (see #5)
7. Check router fire wall (see #3) and Set up Mac address filtering
8. If wireless change your encryption to WPA2 and make you login phrase as long as possible (64 max) and make it a non dictionary (see #5)
*note WPA is not secure any more like many believe its not as bad as wep but getting their if you make the pass non dictionary and as close to 64 chrs as possible the chances of CoWpatty or air crack with JTR working are considerably reduced IE: will take more hours then the average human has to live
9. Check you router logs (DHCP Table ETC...)

If after all this you find some one is hacking you then they have some skills and are targeting you specifically

 

and also keep any hard to remember pass words or delicate files on a thumb drive and encrypt it with true crypt
http://www.truecrypt.org/