Hi Donovansrb10,
The only thing a user should not do is install two "resident" av solutions onto one machine. This brings the same effect as two watch dogs watching a house, they start to fight among each other and not protect the home (computer). It is very well possible to combine one resident av solution with various non-resident or on-demand anti-malware scanners, so I combine avast resident with DrWebCureIt, stinger.exe, RUBotted, ComodoBoClean, MBAM, SAS, SpywareBlaster, A-suared Free as my personal formula (always take care to fully upgrade and update every scanner and do a full scan every fortnight or so).
For Cleansing you could combine it with CCleaner, but I use ATFCleaner and ClearProg.
What you cannot combine is for instance avast resident and symantec resident or mcafee resident or whatever major resident av solution that runs in the background and where the one scanner can interfere or find up the malware signatures of the other (that is why sonme online scanners cannot be combined, because of the open signature files (panda and avast do not go together).
Same story can be told for a software firewall, just use one, two is not better it is worse, when visiting these forums more often these are the very first things the advanced users tell you here, so I will never forget this rule and now you won't either,
polonus