For antivirus and antispyware tools, you should look to tools that offer Enterprise features: they have either a proprietary management console, or use the Micrsoft SuS, now WUS, SMS or MOM.
Antispyware that deals with non-viral, trojan or worm issues, are pre-announced by several companies, including Microsoft, Shavlik, Symantec and soon many others. Essentially this product space is on hold until Microsoft announces in detail their Antispyware plans for this product space. (And related, their plans for antivirus protection, if any, at the local and Enterprise level). Stay tuned.
Original poster deboyland needs to say more about whether in a Domain, Worgroup, stand-alone, or all three, as the support environment he faces. Some of the tools mentioned above, for example, would never be permitted in a managed, Enterprise setting. Some of the tools above, if used by a novice, could easily create more harm than good.
My own personal advice is to go through certification. While there are great test takers that are lousy administrators, the intention at least for the courses is to teach you how to do things well. If you are uncertified, or need additional certifications, ask your employer for financial assistance.
If I hired you, personally, I would pay for your MCSE. While you cannot train experience, as a starting step the industry certifications offered by many: Microst, CISCO, A+, the security groups, etc.. would help you more than a disk with Hijack This or any other tool.
If you were an outside contractor, I would not let you near any of my servers or workstations with the tools mentioned above. You can effectively do this, with experience, in a retail site for stand-alone workstations, but not in a managed setting.